In the Linux kernel, the following vulnerability has been resolved: mm: zswap: fix shrinker NULL crash with cgroup_disable=memory Christian reports a NULL deref in zswap that he bisected down to the zswap shrinker. The issue also cropped up in the bug trackers of libguestfs [1] and the Red Hat bugzilla [2]. The problem is that when memcg is disabled with the boot time flag, the zswap shrinker might get called with sc->memcg == NULL. This is okay in many places, like the lruvec operations. But it crashes in memcg_page_state() - which is only used due to the non-node accounting of cgroup's the zswap memory to begin with. Nhat spotted that the memcg can be NULL in the memcg-disabled case, and I was then able to reproduce the crash locally as well. [1] https://github.com/libguestfs/libguestfs/issues/139 [2] https://bugzilla.redhat.com/show_bug.cgi?id=2275252
In the Linux kernel, the following vulnerability has been resolved: net: phy: micrel: Fix potential null pointer dereference In lan8814_get_sig_rx() and lan8814_get_sig_tx() ptp_parse_header() may return NULL as ptp_header due to abnormal packet type or corrupted packet. Fix this bug by adding ptp_header check. Found by Linux Verification Center (linuxtesting.org) with SVACE.
A null pointer dereference issue was found in the sctp network protocol in net/sctp/stream_sched.c in Linux Kernel. If stream_in allocation is failed, stream_out is freed which would further be accessed. A local user could use this flaw to crash the system or potentially cause a denial of service.
The kvm_arch_vcpu_ioctl_set_sregs function in the KVM in Linux kernel 2.6 before 2.6.30, when running on x86 systems, does not validate the page table root in a KVM_SET_SREGS call, which allows local users to cause a denial of service (crash or hang) via a crafted cr3 value, which triggers a NULL pointer dereference in the gfn_to_rmap function.
A null pointer dereference issue was found in can protocol in net/can/af_can.c in the Linux before Linux. ml_priv may not be initialized in the receive path of CAN frames. A local user could use this flaw to crash the system or potentially cause a denial of service.
A NULL pointer dereference was found in io_file_bitmap_get in io_uring/filetable.c in the io_uring sub-component in the Linux Kernel. When fixed files are unregistered, some context information (file_alloc_{start,end} and alloc_hint) is not cleared. A subsequent request that has auto index selection enabled via IORING_FILE_INDEX_ALLOC can cause a NULL pointer dereference. An unprivileged user can use the flaw to cause a system crash.
Avast and AVG Antivirus for Windows were susceptible to a NULL pointer dereference issue via RPC-interface. The issue was fixed with Avast and AVG Antivirus version 22.11
A vulnerability classified as problematic has been found in Jianming Antivirus 16.2.2022.418. Affected is an unknown function in the library kvcore.sys of the component IoControlCode Handler. The manipulation leads to null pointer dereference. The attack needs to be approached locally. The exploit has been disclosed to the public and may be used. VDB-224010 is the identifier assigned to this vulnerability.
A vulnerability classified as problematic was found in Watchdog Anti-Virus 1.4.214.0. Affected by this vulnerability is the function 0x80002004/0x80002008 in the library wsdk-driver.sys of the component IoControlCode Handler. The manipulation leads to denial of service. An attack has to be approached locally. The exploit has been disclosed to the public and may be used. The associated identifier of this vulnerability is VDB-223291.
A vulnerability, which was classified as problematic, was found in JiangMin Antivirus 16.2.2022.418. This affects the function 0x222010 in the library kvcore.sys of the component IOCTL Handler. The manipulation leads to null pointer dereference. Attacking locally is a requirement. The exploit has been disclosed to the public and may be used. The identifier VDB-224013 was assigned to this vulnerability.
A vulnerability has been found in FabulaTech Webcam for Remote Desktop 2.8.42 and classified as problematic. This vulnerability affects the function 0x222010/0x222018 in the library ftwebcam.sys of the component IOCTL Handler. The manipulation leads to null pointer dereference. Attacking locally is a requirement. The exploit has been disclosed to the public and may be used. VDB-222358 is the identifier assigned to this vulnerability.
In the Linux kernel, the following vulnerability has been resolved: rose: Fix NULL pointer dereference in rose_send_frame() The syzkaller reported an issue: KASAN: null-ptr-deref in range [0x0000000000000380-0x0000000000000387] CPU: 0 PID: 4069 Comm: kworker/0:15 Not tainted 6.0.0-syzkaller-02734-g0326074ff465 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022 Workqueue: rcu_gp srcu_invoke_callbacks RIP: 0010:rose_send_frame+0x1dd/0x2f0 net/rose/rose_link.c:101 Call Trace: <IRQ> rose_transmit_clear_request+0x1d5/0x290 net/rose/rose_link.c:255 rose_rx_call_request+0x4c0/0x1bc0 net/rose/af_rose.c:1009 rose_loopback_timer+0x19e/0x590 net/rose/rose_loopback.c:111 call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers.part.0+0x674/0xa80 kernel/time/timer.c:1790 __run_timers kernel/time/timer.c:1768 [inline] run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1803 __do_softirq+0x1d0/0x9c8 kernel/softirq.c:571 [...] </IRQ> It triggers NULL pointer dereference when 'neigh->dev->dev_addr' is called in the rose_send_frame(). It's the first occurrence of the `neigh` is in rose_loopback_timer() as `rose_loopback_neigh', and the 'dev' in 'rose_loopback_neigh' is initialized sa nullptr. It had been fixed by commit 3b3fd068c56e3fbea30090859216a368398e39bf ("rose: Fix Null pointer dereference in rose_send_frame()") ever. But it's introduced by commit 3c53cd65dece47dd1f9d3a809f32e59d1d87b2b8 ("rose: check NULL rose_loopback_neigh->loopback") again. We fix it by add NULL check in rose_transmit_clear_request(). When the 'dev' in 'neigh' is NULL, we don't reply the request and just clear it. syzkaller don't provide repro, and I provide a syz repro like: r0 = syz_init_net_socket$bt_sco(0x1f, 0x5, 0x2) ioctl$sock_inet_SIOCSIFFLAGS(r0, 0x8914, &(0x7f0000000180)={'rose0\x00', 0x201}) r1 = syz_init_net_socket$rose(0xb, 0x5, 0x0) bind$rose(r1, &(0x7f00000000c0)=@full={0xb, @dev, @null, 0x0, [@null, @null, @netrom, @netrom, @default, @null]}, 0x40) connect$rose(r1, &(0x7f0000000240)=@short={0xb, @dev={0xbb, 0xbb, 0xbb, 0x1, 0x0}, @remote={0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0x1}, 0x1, @netrom={0xbb, 0xbb, 0xbb, 0xbb, 0xbb, 0x0, 0x0}}, 0x1c)
In the Linux kernel, the following vulnerability has been resolved: IB/hfi1: Correctly move list in sc_disable() Commit 13bac861952a ("IB/hfi1: Fix abba locking issue with sc_disable()") incorrectly tries to move a list from one list head to another. The result is a kernel crash. The crash is triggered when a link goes down and there are waiters for a send to complete. The following signature is seen: BUG: kernel NULL pointer dereference, address: 0000000000000030 [...] Call Trace: sc_disable+0x1ba/0x240 [hfi1] pio_freeze+0x3d/0x60 [hfi1] handle_freeze+0x27/0x1b0 [hfi1] process_one_work+0x1b0/0x380 ? process_one_work+0x380/0x380 worker_thread+0x30/0x360 ? process_one_work+0x380/0x380 kthread+0xd7/0x100 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x1f/0x30 The fix is to use the correct call to move the list.
In the Linux kernel, the following vulnerability has been resolved: net, neigh: Fix null-ptr-deref in neigh_table_clear() When IPv6 module gets initialized but hits an error in the middle, kenel panic with: KASAN: null-ptr-deref in range [0x0000000000000598-0x000000000000059f] CPU: 1 PID: 361 Comm: insmod Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:__neigh_ifdown.isra.0+0x24b/0x370 RSP: 0018:ffff888012677908 EFLAGS: 00000202 ... Call Trace: <TASK> neigh_table_clear+0x94/0x2d0 ndisc_cleanup+0x27/0x40 [ipv6] inet6_init+0x21c/0x2cb [ipv6] do_one_initcall+0xd3/0x4d0 do_init_module+0x1ae/0x670 ... Kernel panic - not syncing: Fatal exception When ipv6 initialization fails, it will try to cleanup and calls: neigh_table_clear() neigh_ifdown(tbl, NULL) pneigh_queue_purge(&tbl->proxy_queue, dev_net(dev == NULL)) # dev_net(NULL) triggers null-ptr-deref. Fix it by passing NULL to pneigh_queue_purge() in neigh_ifdown() if dev is NULL, to make kernel not panic immediately.
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Fix null-ptr-deref when xps sysfs alloc failed There is a null-ptr-deref when xps sysfs alloc failed: BUG: KASAN: null-ptr-deref in sysfs_do_create_link_sd+0x40/0xd0 Read of size 8 at addr 0000000000000030 by task gssproxy/457 CPU: 5 PID: 457 Comm: gssproxy Not tainted 6.0.0-09040-g02357b27ee03 #9 Call Trace: <TASK> dump_stack_lvl+0x34/0x44 kasan_report+0xa3/0x120 sysfs_do_create_link_sd+0x40/0xd0 rpc_sysfs_client_setup+0x161/0x1b0 rpc_new_client+0x3fc/0x6e0 rpc_create_xprt+0x71/0x220 rpc_create+0x1d4/0x350 gssp_rpc_create+0xc3/0x160 set_gssp_clnt+0xbc/0x140 write_gssp+0x116/0x1a0 proc_reg_write+0xd6/0x130 vfs_write+0x177/0x690 ksys_write+0xb9/0x150 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 When the xprt_switch sysfs alloc failed, should not add xprt and switch sysfs to it, otherwise, maybe null-ptr-deref; also initialize the 'xps_sysfs' to NULL to avoid oops when destroy it.
In the Linux kernel, the following vulnerability has been resolved: net: phy: at803x: fix NULL pointer dereference on AR9331 PHY Latest kernel will explode on the PHY interrupt config, since it depends now on allocated priv. So, run probe to allocate priv to fix it. ar9331_switch ethernet.1:10 lan0 (uninitialized): PHY [!ahb!ethernet@1a000000!mdio!switch@10:00] driver [Qualcomm Atheros AR9331 built-in PHY] (irq=13) CPU 0 Unable to handle kernel paging request at virtual address 0000000a, epc == 8050e8a8, ra == 80504b34 ... Call Trace: [<8050e8a8>] at803x_config_intr+0x5c/0xd0 [<80504b34>] phy_request_interrupt+0xa8/0xd0 [<8050289c>] phylink_bringup_phy+0x2d8/0x3ac [<80502b68>] phylink_fwnode_phy_connect+0x118/0x130 [<8074d8ec>] dsa_slave_create+0x270/0x420 [<80743b04>] dsa_port_setup+0x12c/0x148 [<8074580c>] dsa_register_switch+0xaf0/0xcc0 [<80511344>] ar9331_sw_probe+0x370/0x388 [<8050cb78>] mdio_probe+0x44/0x70 [<804df300>] really_probe+0x200/0x424 [<804df7b4>] __driver_probe_device+0x290/0x298 [<804df810>] driver_probe_device+0x54/0xe4 [<804dfd50>] __device_attach_driver+0xe4/0x130 [<804dcb00>] bus_for_each_drv+0xb4/0xd8 [<804dfac4>] __device_attach+0x104/0x1a4 [<804ddd24>] bus_probe_device+0x48/0xc4 [<804deb44>] deferred_probe_work_func+0xf0/0x10c [<800a0ffc>] process_one_work+0x314/0x4d4 [<800a17fc>] worker_thread+0x2a4/0x354 [<800a9a54>] kthread+0x134/0x13c [<8006306c>] ret_from_kernel_thread+0x14/0x1c Same Issue would affect some other PHYs (QCA8081, QCA9561), so fix it too.
In the Linux kernel, the following vulnerability has been resolved: scsi: ibmvfc: Store vhost pointer during subcrq allocation Currently the back pointer from a queue to the vhost adapter isn't set until after subcrq interrupt registration. The value is available when a queue is first allocated and can/should be also set for primary and async queues as well as subcrqs. This fixes a crash observed during kexec/kdump on Power 9 with legacy XICS interrupt controller where a pending subcrq interrupt from the previous kernel can be replayed immediately upon IRQ registration resulting in dereference of a garbage backpointer in ibmvfc_interrupt_scsi(). Kernel attempted to read user page (58) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x00000058 Faulting instruction address: 0xc008000003216a08 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP [c008000003216a08] ibmvfc_interrupt_scsi+0x40/0xb0 [ibmvfc] LR [c0000000082079e8] __handle_irq_event_percpu+0x98/0x270 Call Trace: [c000000047fa3d80] [c0000000123e6180] 0xc0000000123e6180 (unreliable) [c000000047fa3df0] [c0000000082079e8] __handle_irq_event_percpu+0x98/0x270 [c000000047fa3ea0] [c000000008207d18] handle_irq_event+0x98/0x188 [c000000047fa3ef0] [c00000000820f564] handle_fasteoi_irq+0xc4/0x310 [c000000047fa3f40] [c000000008205c60] generic_handle_irq+0x50/0x80 [c000000047fa3f60] [c000000008015c40] __do_irq+0x70/0x1a0 [c000000047fa3f90] [c000000008016d7c] __do_IRQ+0x9c/0x130 [c000000014622f60] [0000000020000000] 0x20000000 [c000000014622ff0] [c000000008016e50] do_IRQ+0x40/0xa0 [c000000014623020] [c000000008017044] replay_soft_interrupts+0x194/0x2f0 [c000000014623210] [c0000000080172a8] arch_local_irq_restore+0x108/0x170 [c000000014623240] [c000000008eb1008] _raw_spin_unlock_irqrestore+0x58/0xb0 [c000000014623270] [c00000000820b12c] __setup_irq+0x49c/0x9f0 [c000000014623310] [c00000000820b7c0] request_threaded_irq+0x140/0x230 [c000000014623380] [c008000003212a50] ibmvfc_register_scsi_channel+0x1e8/0x2f0 [ibmvfc] [c000000014623450] [c008000003213d1c] ibmvfc_init_sub_crqs+0xc4/0x1f0 [ibmvfc] [c0000000146234d0] [c0080000032145a8] ibmvfc_reset_crq+0x150/0x210 [ibmvfc] [c000000014623550] [c0080000032147c8] ibmvfc_init_crq+0x160/0x280 [ibmvfc] [c0000000146235f0] [c00800000321a9cc] ibmvfc_probe+0x2a4/0x530 [ibmvfc]
In the Linux kernel, the following vulnerability has been resolved: bpftool: Fix NULL pointer dereference when pin {PROG, MAP, LINK} without FILE When using bpftool to pin {PROG, MAP, LINK} without FILE, segmentation fault will occur. The reson is that the lack of FILE will cause strlen to trigger NULL pointer dereference. The corresponding stacktrace is shown below: do_pin do_pin_any do_pin_fd mount_bpffs_for_pin strlen(name) <- NULL pointer dereference Fix it by adding validation to the common process.
In the Linux kernel, the following vulnerability has been resolved: drm/amdkfd: Fix NULL pointer dereference in svm_migrate_to_ram() ./drivers/gpu/drm/amd/amdkfd/kfd_migrate.c:985:58-62: ERROR: p is NULL but dereferenced.
In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: fix general-protection-fault in ieee80211_subif_start_xmit() When device is running and the interface status is changed, the gpf issue is triggered. The problem triggering process is as follows: Thread A: Thread B ieee80211_runtime_change_iftype() process_one_work() ... ... ieee80211_do_stop() ... ... ... sdata->bss = NULL ... ... ieee80211_subif_start_xmit() ieee80211_multicast_to_unicast //!sdata->bss->multicast_to_unicast cause gpf issue When the interface status is changed, the sending queue continues to send packets. After the bss is set to NULL, the bss is accessed. As a result, this causes a general-protection-fault issue. The following is the stack information: general protection fault, probably for non-canonical address 0xdffffc000000002f: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000178-0x000000000000017f] Workqueue: mld mld_ifc_work RIP: 0010:ieee80211_subif_start_xmit+0x25b/0x1310 Call Trace: <TASK> dev_hard_start_xmit+0x1be/0x990 __dev_queue_xmit+0x2c9a/0x3b60 ip6_finish_output2+0xf92/0x1520 ip6_finish_output+0x6af/0x11e0 ip6_output+0x1ed/0x540 mld_sendpack+0xa09/0xe70 mld_ifc_work+0x71c/0xdb0 process_one_work+0x9bf/0x1710 worker_thread+0x665/0x1080 kthread+0x2e4/0x3a0 ret_from_fork+0x1f/0x30 </TASK>
An issue was discovered in OpenEXR before 2.5.2. An invalid tiled input file could cause invalid memory access in TiledInputFile::TiledInputFile() in IlmImf/ImfTiledInputFile.cpp, as demonstrated by a NULL pointer dereference.
In the Linux kernel, the following vulnerability has been resolved: RDMA/hns: Fix NULL pointer problem in free_mr_init() Lock grab occurs in a concurrent scenario, resulting in stepping on a NULL pointer. It should be init mutex_init() first before use the lock. Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Call trace: __mutex_lock.constprop.0+0xd0/0x5c0 __mutex_lock_slowpath+0x1c/0x2c mutex_lock+0x44/0x50 free_mr_send_cmd_to_hw+0x7c/0x1c0 [hns_roce_hw_v2] hns_roce_v2_dereg_mr+0x30/0x40 [hns_roce_hw_v2] hns_roce_dereg_mr+0x4c/0x130 [hns_roce_hw_v2] ib_dereg_mr_user+0x54/0x124 uverbs_free_mr+0x24/0x30 destroy_hw_idr_uobject+0x38/0x74 uverbs_destroy_uobject+0x48/0x1c4 uobj_destroy+0x74/0xcc ib_uverbs_cmd_verbs+0x368/0xbb0 ib_uverbs_ioctl+0xec/0x1a4 __arm64_sys_ioctl+0xb4/0x100 invoke_syscall+0x50/0x120 el0_svc_common.constprop.0+0x58/0x190 do_el0_svc+0x30/0x90 el0_svc+0x2c/0xb4 el0t_64_sync_handler+0x1a4/0x1b0 el0t_64_sync+0x19c/0x1a0
In the Linux kernel, the following vulnerability has been resolved: pinctrl: renesas: rzn1: Fix possible null-ptr-deref in sh_pfc_map_resources() It will cause null-ptr-deref when using 'res', if platform_get_resource() returns NULL, so move using 'res' after devm_ioremap_resource() that will check it to avoid null-ptr-deref. And use devm_platform_get_and_ioremap_resource() to simplify code.
In the Linux kernel, the following vulnerability has been resolved: media: venus: hfi: avoid null dereference in deinit If venus_probe fails at pm_runtime_put_sync the error handling first calls hfi_destroy and afterwards hfi_core_deinit. As hfi_destroy sets core->ops to NULL, hfi_core_deinit cannot call the core_deinit function anymore. Avoid this null pointer derefence by skipping the call when necessary.
In the Linux kernel, the following vulnerability has been resolved: net: ethernet: stmmac: fix altr_tse_pcs function when using a fixed-link When using a fixed-link, the altr_tse_pcs driver crashes due to null-pointer dereference as no phy_device is provided to tse_pcs_fix_mac_speed function. Fix this by adding a check for phy_dev before calling the tse_pcs_fix_mac_speed() function. Also clean up the tse_pcs_fix_mac_speed function a bit. There is no need to check for splitter_base and sgmii_adapter_base because the driver will fail if these 2 variables are not derived from the device tree.
In the Linux kernel, the following vulnerability has been resolved: drm/rockchip: vop: fix possible null-ptr-deref in vop_bind() It will cause null-ptr-deref in resource_size(), if platform_get_resource() returns NULL, move calling resource_size() after devm_ioremap_resource() that will check 'res' to avoid null-ptr-deref.
In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu/cs: make commands with 0 chunks illegal behaviour. Submitting a cs with 0 chunks, causes an oops later, found trying to execute the wrong userspace driver. MESA_LOADER_DRIVER_OVERRIDE=v3d glxinfo [172536.665184] BUG: kernel NULL pointer dereference, address: 00000000000001d8 [172536.665188] #PF: supervisor read access in kernel mode [172536.665189] #PF: error_code(0x0000) - not-present page [172536.665191] PGD 6712a0067 P4D 6712a0067 PUD 5af9ff067 PMD 0 [172536.665195] Oops: 0000 [#1] SMP NOPTI [172536.665197] CPU: 7 PID: 2769838 Comm: glxinfo Tainted: P O 5.10.81 #1-NixOS [172536.665199] Hardware name: To be filled by O.E.M. To be filled by O.E.M./CROSSHAIR V FORMULA-Z, BIOS 2201 03/23/2015 [172536.665272] RIP: 0010:amdgpu_cs_ioctl+0x96/0x1ce0 [amdgpu] [172536.665274] Code: 75 18 00 00 4c 8b b2 88 00 00 00 8b 46 08 48 89 54 24 68 49 89 f7 4c 89 5c 24 60 31 d2 4c 89 74 24 30 85 c0 0f 85 c0 01 00 00 <48> 83 ba d8 01 00 00 00 48 8b b4 24 90 00 00 00 74 16 48 8b 46 10 [172536.665276] RSP: 0018:ffffb47c0e81bbe0 EFLAGS: 00010246 [172536.665277] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [172536.665278] RDX: 0000000000000000 RSI: ffffb47c0e81be28 RDI: ffffb47c0e81bd68 [172536.665279] RBP: ffff936524080010 R08: 0000000000000000 R09: ffffb47c0e81be38 [172536.665281] R10: ffff936524080010 R11: ffff936524080000 R12: ffffb47c0e81bc40 [172536.665282] R13: ffffb47c0e81be28 R14: ffff9367bc410000 R15: ffffb47c0e81be28 [172536.665283] FS: 00007fe35e05d740(0000) GS:ffff936c1edc0000(0000) knlGS:0000000000000000 [172536.665284] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [172536.665286] CR2: 00000000000001d8 CR3: 0000000532e46000 CR4: 00000000000406e0 [172536.665287] Call Trace: [172536.665322] ? amdgpu_cs_find_mapping+0x110/0x110 [amdgpu] [172536.665332] drm_ioctl_kernel+0xaa/0xf0 [drm] [172536.665338] drm_ioctl+0x201/0x3b0 [drm] [172536.665369] ? amdgpu_cs_find_mapping+0x110/0x110 [amdgpu] [172536.665372] ? selinux_file_ioctl+0x135/0x230 [172536.665399] amdgpu_drm_ioctl+0x49/0x80 [amdgpu] [172536.665403] __x64_sys_ioctl+0x83/0xb0 [172536.665406] do_syscall_64+0x33/0x40 [172536.665409] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/2018
In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Fix a NULL pointer dereference in amdgpu_dm_connector_add_common_modes() In amdgpu_dm_connector_add_common_modes(), amdgpu_dm_create_common_mode() is assigned to mode and is passed to drm_mode_probed_add() directly after that. drm_mode_probed_add() passes &mode->head to list_add_tail(), and there is a dereference of it in list_add_tail() without recoveries, which could lead to NULL pointer dereference on failure of amdgpu_dm_create_common_mode(). Fix this by adding a NULL check of mode. This bug was found by a static analyzer. Builds with 'make allyesconfig' show no new warnings, and our static analyzer no longer warns about this code.
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Fix the svc_deferred_event trace class Fix a NULL deref crash that occurs when an svc_rqst is deferred while the sunrpc tracing subsystem is enabled. svc_revisit() sets dr->xprt to NULL, so it can't be relied upon in the tracepoint to provide the remote's address. Unfortunately we can't revert the "svc_deferred_class" hunk in commit ece200ddd54b ("sunrpc: Save remote presentation address in svc_xprt for trace events") because there is now a specific check of event format specifiers for unsafe dereferences. The warning that check emits is: event svc_defer_recv has unsafe dereference of argument 1 A "%pISpc" format specifier with a "struct sockaddr *" is indeed flagged by this check. Instead, take the brute-force approach used by the svcrdma_qp_error tracepoint. Convert the dr::addr field into a presentation address in the TP_fast_assign() arm of the trace event, and store that as a string. This fix can be backported to -stable kernels. In the meantime, commit c6ced22997ad ("tracing: Update print fmt check to handle new __get_sockaddr() macro") is now in v5.18, so this wonky fix can be replaced with __sockaddr() and friends properly during the v5.19 merge window.
In the Linux kernel, the following vulnerability has been resolved: drm/v3d: Fix null pointer dereference of pointer perfmon In the unlikely event that pointer perfmon is null the WARN_ON return path occurs after the pointer has already been deferenced. Fix this by only dereferencing perfmon after it has been null checked.
In the Linux kernel, the following vulnerability has been resolved: rtc: cmos: Fix event handler registration ordering issue Because acpi_install_fixed_event_handler() enables the event automatically on success, it is incorrect to call it before the handler routine passed to it is ready to handle events. Unfortunately, the rtc-cmos driver does exactly the incorrect thing by calling cmos_wake_setup(), which passes rtc_handler() to acpi_install_fixed_event_handler(), before cmos_do_probe(), because rtc_handler() uses dev_get_drvdata() to get to the cmos object pointer and the driver data pointer is only populated in cmos_do_probe(). This leads to a NULL pointer dereference in rtc_handler() on boot if the RTC fixed event happens to be active at the init time. To address this issue, change the initialization ordering of the driver so that cmos_wake_setup() is always called after a successful cmos_do_probe() call. While at it, change cmos_pnp_probe() to call cmos_do_probe() after the initial if () statement used for computing the IRQ argument to be passed to cmos_do_probe() which is cleaner than calling it in each branch of that if () (local variable "irq" can be of type int, because it is passed to that function as an argument of type int). Note that commit 6492fed7d8c9 ("rtc: rtc-cmos: Do not check ACPI_FADT_LOW_POWER_S0") caused this issue to affect a larger number of systems, because previously it only affected systems with ACPI_FADT_LOW_POWER_S0 set, but it is present regardless of that commit.
In the Linux kernel, the following vulnerability has been resolved: drm/msm/disp/dpu1: avoid clearing hw interrupts if hw_intr is null during drm uninit If edp modeset init is failed due to panel being not ready and probe defers during drm bind, avoid clearing irqs and dereference hw_intr when hw_intr is null. BUG: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Call trace: dpu_core_irq_uninstall+0x50/0xb0 dpu_irq_uninstall+0x18/0x24 msm_drm_uninit+0xd8/0x16c msm_drm_bind+0x580/0x5fc try_to_bring_up_master+0x168/0x1c0 __component_add+0xb4/0x178 component_add+0x1c/0x28 dp_display_probe+0x38c/0x400 platform_probe+0xb0/0xd0 really_probe+0xcc/0x2c8 __driver_probe_device+0xbc/0xe8 driver_probe_device+0x48/0xf0 __device_attach_driver+0xa0/0xc8 bus_for_each_drv+0x8c/0xd8 __device_attach+0xc4/0x150 device_initial_probe+0x1c/0x28 Changes in V2: - Update commit message and coreect fixes tag. Patchwork: https://patchwork.freedesktop.org/patch/484430/
In the Linux kernel, the following vulnerability has been resolved: drm/msm: Fix null pointer dereferences without iommu Check if 'aspace' is set before using it as it will stay null without IOMMU, such as on msm8974.
In the Linux kernel, the following vulnerability has been resolved: ice: always check VF VSI pointer values The ice_get_vf_vsi function can return NULL in some cases, such as if handling messages during a reset where the VSI is being removed and recreated. Several places throughout the driver do not bother to check whether this VSI pointer is valid. Static analysis tools maybe report issues because they detect paths where a potentially NULL pointer could be dereferenced. Fix this by checking the return value of ice_get_vf_vsi everywhere.
In the Linux kernel, the following vulnerability has been resolved: mac802154: fix missing INIT_LIST_HEAD in ieee802154_if_add() Kernel fault injection test reports null-ptr-deref as follows: BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:cfg802154_netdev_notifier_call+0x120/0x310 include/linux/list.h:114 Call Trace: <TASK> raw_notifier_call_chain+0x6d/0xa0 kernel/notifier.c:87 call_netdevice_notifiers_info+0x6e/0xc0 net/core/dev.c:1944 unregister_netdevice_many_notify+0x60d/0xcb0 net/core/dev.c:1982 unregister_netdevice_queue+0x154/0x1a0 net/core/dev.c:10879 register_netdevice+0x9a8/0xb90 net/core/dev.c:10083 ieee802154_if_add+0x6ed/0x7e0 net/mac802154/iface.c:659 ieee802154_register_hw+0x29c/0x330 net/mac802154/main.c:229 mcr20a_probe+0xaaa/0xcb1 drivers/net/ieee802154/mcr20a.c:1316 ieee802154_if_add() allocates wpan_dev as netdev's private data, but not init the list in struct wpan_dev. cfg802154_netdev_notifier_call() manage the list when device register/unregister, and may lead to null-ptr-deref. Use INIT_LIST_HEAD() on it to initialize it correctly.
In the Linux kernel, the following vulnerability has been resolved: drm/msm/dsi: invalid parameter check in msm_dsi_phy_enable The function performs a check on the "phy" input parameter, however, it is used before the check. Initialize the "dev" variable after the sanity check to avoid a possible NULL pointer dereference. Addresses-Coverity-ID: 1493860 ("Null pointer dereference")
In the Linux kernel, the following vulnerability has been resolved: tty: synclink_gt: Fix null-pointer-dereference in slgt_clean() When the driver fails at alloc_hdlcdev(), and then we remove the driver module, we will get the following splat: [ 25.065966] general protection fault, probably for non-canonical address 0xdffffc0000000182: 0000 [#1] PREEMPT SMP KASAN PTI [ 25.066914] KASAN: null-ptr-deref in range [0x0000000000000c10-0x0000000000000c17] [ 25.069262] RIP: 0010:detach_hdlc_protocol+0x2a/0x3e0 [ 25.077709] Call Trace: [ 25.077924] <TASK> [ 25.078108] unregister_hdlc_device+0x16/0x30 [ 25.078481] slgt_cleanup+0x157/0x9f0 [synclink_gt] Fix this by checking whether the 'info->netdev' is a null pointer first.
In the Linux kernel, the following vulnerability has been resolved: iommu/arm-smmu-v3: Don't unregister on shutdown Similar to SMMUv2, this driver calls iommu_device_unregister() from the shutdown path, which removes the IOMMU groups with no coordination whatsoever with their users - shutdown methods are optional in device drivers. This can lead to NULL pointer dereferences in those drivers' DMA API calls, or worse. Instead of calling the full arm_smmu_device_remove() from arm_smmu_device_shutdown(), let's pick only the relevant function call - arm_smmu_device_disable() - more or less the reverse of arm_smmu_device_reset() - and call just that from the shutdown path.
In the Linux kernel, the following vulnerability has been resolved: md: Don't set mddev private to NULL in raid0 pers->free In normal stop process, it does like this: do_md_stop | __md_stop (pers->free(); mddev->private=NULL) | md_free (free mddev) __md_stop sets mddev->private to NULL after pers->free. The raid device will be stopped and mddev memory is free. But in reshape, it doesn't free the mddev and mddev will still be used in new raid. In reshape, it first sets mddev->private to new_pers and then runs old_pers->free(). Now raid0 sets mddev->private to NULL in raid0_free. The new raid can't work anymore. It will panic when dereference mddev->private because of NULL pointer dereference. It can panic like this: [63010.814972] kernel BUG at drivers/md/raid10.c:928! [63010.819778] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI [63010.825011] CPU: 3 PID: 44437 Comm: md0_resync Kdump: loaded Not tainted 5.14.0-86.el9.x86_64 #1 [63010.833789] Hardware name: Dell Inc. PowerEdge R6415/07YXFK, BIOS 1.15.0 09/11/2020 [63010.841440] RIP: 0010:raise_barrier+0x161/0x170 [raid10] [63010.865508] RSP: 0018:ffffc312408bbc10 EFLAGS: 00010246 [63010.870734] RAX: 0000000000000000 RBX: ffffa00bf7d39800 RCX: 0000000000000000 [63010.877866] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffa00bf7d39800 [63010.884999] RBP: 0000000000000000 R08: fffffa4945e74400 R09: 0000000000000000 [63010.892132] R10: ffffa00eed02f798 R11: 0000000000000000 R12: ffffa00bbc435200 [63010.899266] R13: ffffa00bf7d39800 R14: 0000000000000400 R15: 0000000000000003 [63010.906399] FS: 0000000000000000(0000) GS:ffffa00eed000000(0000) knlGS:0000000000000000 [63010.914485] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [63010.920229] CR2: 00007f5cfbe99828 CR3: 0000000105efe000 CR4: 00000000003506e0 [63010.927363] Call Trace: [63010.929822] ? bio_reset+0xe/0x40 [63010.933144] ? raid10_alloc_init_r10buf+0x60/0xa0 [raid10] [63010.938629] raid10_sync_request+0x756/0x1610 [raid10] [63010.943770] md_do_sync.cold+0x3e4/0x94c [63010.947698] md_thread+0xab/0x160 [63010.951024] ? md_write_inc+0x50/0x50 [63010.954688] kthread+0x149/0x170 [63010.957923] ? set_kthread_struct+0x40/0x40 [63010.962107] ret_from_fork+0x22/0x30 Removing the code that sets mddev->private to NULL in raid0 can fix problem.
In the Linux kernel, the following vulnerability has been resolved: vduse: Fix NULL pointer dereference on sysfs access The control device has no drvdata. So we will get a NULL pointer dereference when accessing control device's msg_timeout attribute via sysfs: [ 132.841881][ T3644] BUG: kernel NULL pointer dereference, address: 00000000000000f8 [ 132.850619][ T3644] RIP: 0010:msg_timeout_show (drivers/vdpa/vdpa_user/vduse_dev.c:1271) [ 132.869447][ T3644] dev_attr_show (drivers/base/core.c:2094) [ 132.870215][ T3644] sysfs_kf_seq_show (fs/sysfs/file.c:59) [ 132.871164][ T3644] ? device_remove_bin_file (drivers/base/core.c:2088) [ 132.872082][ T3644] kernfs_seq_show (fs/kernfs/file.c:164) [ 132.872838][ T3644] seq_read_iter (fs/seq_file.c:230) [ 132.873578][ T3644] ? __vmalloc_area_node (mm/vmalloc.c:3041) [ 132.874532][ T3644] kernfs_fop_read_iter (fs/kernfs/file.c:238) [ 132.875513][ T3644] __kernel_read (fs/read_write.c:440 (discriminator 1)) [ 132.876319][ T3644] kernel_read (fs/read_write.c:459) [ 132.877129][ T3644] kernel_read_file (fs/kernel_read_file.c:94) [ 132.877978][ T3644] kernel_read_file_from_fd (include/linux/file.h:45 fs/kernel_read_file.c:186) [ 132.879019][ T3644] __do_sys_finit_module (kernel/module.c:4207) [ 132.879930][ T3644] __ia32_sys_finit_module (kernel/module.c:4189) [ 132.880930][ T3644] do_int80_syscall_32 (arch/x86/entry/common.c:112 arch/x86/entry/common.c:132) [ 132.881847][ T3644] entry_INT80_compat (arch/x86/entry/entry_64_compat.S:419) To fix it, don't create the unneeded attribute for control device anymore.
In the Linux kernel, the following vulnerability has been resolved: net: sparx5: switchdev: fix possible NULL pointer dereference As the possible failure of the allocation, devm_kzalloc() may return NULL pointer. Therefore, it should be better to check the 'db' in order to prevent the dereference of NULL pointer.
In the Linux kernel, the following vulnerability has been resolved: KVM: Don't null dereference ops->destroy A KVM device cleanup happens in either of two callbacks: 1) destroy() which is called when the VM is being destroyed; 2) release() which is called when a device fd is closed. Most KVM devices use 1) but Book3s's interrupt controller KVM devices (XICS, XIVE, XIVE-native) use 2) as they need to close and reopen during the machine execution. The error handling in kvm_ioctl_create_device() assumes destroy() is always defined which leads to NULL dereference as discovered by Syzkaller. This adds a checks for destroy!=NULL and adds a missing release(). This is not changing kvm_destroy_devices() as devices with defined release() should have been removed from the KVM devices list by then.
In the Linux kernel, the following vulnerability has been resolved: xprtrdma: treat all calls not a bcall when bc_serv is NULL When a rdma server returns a fault format reply, nfs v3 client may treats it as a bcall when bc service is not exist. The debug message at rpcrdma_bc_receive_call are, [56579.837169] RPC: rpcrdma_bc_receive_call: callback XID 00000001, length=20 [56579.837174] RPC: rpcrdma_bc_receive_call: 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 04 After that, rpcrdma_bc_receive_call will meets NULL pointer as, [ 226.057890] BUG: unable to handle kernel NULL pointer dereference at 00000000000000c8 ... [ 226.058704] RIP: 0010:_raw_spin_lock+0xc/0x20 ... [ 226.059732] Call Trace: [ 226.059878] rpcrdma_bc_receive_call+0x138/0x327 [rpcrdma] [ 226.060011] __ib_process_cq+0x89/0x170 [ib_core] [ 226.060092] ib_cq_poll_work+0x26/0x80 [ib_core] [ 226.060257] process_one_work+0x1a7/0x360 [ 226.060367] ? create_worker+0x1a0/0x1a0 [ 226.060440] worker_thread+0x30/0x390 [ 226.060500] ? create_worker+0x1a0/0x1a0 [ 226.060574] kthread+0x116/0x130 [ 226.060661] ? kthread_flush_work_fn+0x10/0x10 [ 226.060724] ret_from_fork+0x35/0x40 ...
In the Linux kernel, the following vulnerability has been resolved: soc: bcm: Check for NULL return of devm_kzalloc() As the potential failure of allocation, devm_kzalloc() may return NULL. Then the 'pd->pmb' and the follow lines of code may bring null pointer dereference. Therefore, it is better to check the return value of devm_kzalloc() to avoid this confusion.
In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix NULL pointer dereference in nilfs_palloc_commit_free_entry() Syzbot reported a null-ptr-deref bug: NILFS (loop0): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 1 PID: 3603 Comm: segctord Not tainted 6.1.0-rc2-syzkaller-00105-gb229b6ca5abb #0 Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 RIP: 0010:nilfs_palloc_commit_free_entry+0xe5/0x6b0 fs/nilfs2/alloc.c:608 Code: 00 00 00 00 fc ff df 80 3c 02 00 0f 85 cd 05 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 73 08 49 8d 7e 10 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 26 05 00 00 49 8b 46 10 be a6 00 00 00 48 c7 c7 RSP: 0018:ffffc90003dff830 EFLAGS: 00010212 RAX: dffffc0000000000 RBX: ffff88802594e218 RCX: 000000000000000d RDX: 0000000000000002 RSI: 0000000000002000 RDI: 0000000000000010 RBP: ffff888071880222 R08: 0000000000000005 R09: 000000000000003f R10: 000000000000000d R11: 0000000000000000 R12: ffff888071880158 R13: ffff88802594e220 R14: 0000000000000000 R15: 0000000000000004 FS: 0000000000000000(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb1c08316a8 CR3: 0000000018560000 CR4: 0000000000350ee0 Call Trace: <TASK> nilfs_dat_commit_free fs/nilfs2/dat.c:114 [inline] nilfs_dat_commit_end+0x464/0x5f0 fs/nilfs2/dat.c:193 nilfs_dat_commit_update+0x26/0x40 fs/nilfs2/dat.c:236 nilfs_btree_commit_update_v+0x87/0x4a0 fs/nilfs2/btree.c:1940 nilfs_btree_commit_propagate_v fs/nilfs2/btree.c:2016 [inline] nilfs_btree_propagate_v fs/nilfs2/btree.c:2046 [inline] nilfs_btree_propagate+0xa00/0xd60 fs/nilfs2/btree.c:2088 nilfs_bmap_propagate+0x73/0x170 fs/nilfs2/bmap.c:337 nilfs_collect_file_data+0x45/0xd0 fs/nilfs2/segment.c:568 nilfs_segctor_apply_buffers+0x14a/0x470 fs/nilfs2/segment.c:1018 nilfs_segctor_scan_file+0x3f4/0x6f0 fs/nilfs2/segment.c:1067 nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1197 [inline] nilfs_segctor_collect fs/nilfs2/segment.c:1503 [inline] nilfs_segctor_do_construct+0x12fc/0x6af0 fs/nilfs2/segment.c:2045 nilfs_segctor_construct+0x8e3/0xb30 fs/nilfs2/segment.c:2379 nilfs_segctor_thread_construct fs/nilfs2/segment.c:2487 [inline] nilfs_segctor_thread+0x3c3/0xf30 fs/nilfs2/segment.c:2570 kthread+0x2e4/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 </TASK> ... If DAT metadata file is corrupted on disk, there is a case where req->pr_desc_bh is NULL and blocknr is 0 at nilfs_dat_commit_end() during a b-tree operation that cascadingly updates ancestor nodes of the b-tree, because nilfs_dat_commit_alloc() for a lower level block can initialize the blocknr on the same DAT entry between nilfs_dat_prepare_end() and nilfs_dat_commit_end(). If this happens, nilfs_dat_commit_end() calls nilfs_dat_commit_free() without valid buffer heads in req->pr_desc_bh and req->pr_bitmap_bh, and causes the NULL pointer dereference above in nilfs_palloc_commit_free_entry() function, which leads to a crash. Fix this by adding a NULL check on req->pr_desc_bh and req->pr_bitmap_bh before nilfs_palloc_commit_free_entry() in nilfs_dat_commit_free(). This also calls nilfs_error() in that case to notify that there is a fatal flaw in the filesystem metadata and prevent further operations.
In the Linux kernel, the following vulnerability has been resolved: drm/virtio: fix NULL pointer dereference in virtio_gpu_conn_get_modes drm_cvt_mode may return NULL and we should check it. This bug is found by syzkaller: FAULT_INJECTION stacktrace: [ 168.567394] FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 1 [ 168.567403] CPU: 1 PID: 6425 Comm: syz Kdump: loaded Not tainted 4.19.90-vhulk2201.1.0.h1035.kasan.eulerosv2r10.aarch64 #1 [ 168.567406] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 [ 168.567408] Call trace: [ 168.567414] dump_backtrace+0x0/0x310 [ 168.567418] show_stack+0x28/0x38 [ 168.567423] dump_stack+0xec/0x15c [ 168.567427] should_fail+0x3ac/0x3d0 [ 168.567437] __should_failslab+0xb8/0x120 [ 168.567441] should_failslab+0x28/0xc0 [ 168.567445] kmem_cache_alloc_trace+0x50/0x640 [ 168.567454] drm_mode_create+0x40/0x90 [ 168.567458] drm_cvt_mode+0x48/0xc78 [ 168.567477] virtio_gpu_conn_get_modes+0xa8/0x140 [virtio_gpu] [ 168.567485] drm_helper_probe_single_connector_modes+0x3a4/0xd80 [ 168.567492] drm_mode_getconnector+0x2e0/0xa70 [ 168.567496] drm_ioctl_kernel+0x11c/0x1d8 [ 168.567514] drm_ioctl+0x558/0x6d0 [ 168.567522] do_vfs_ioctl+0x160/0xf30 [ 168.567525] ksys_ioctl+0x98/0xd8 [ 168.567530] __arm64_sys_ioctl+0x50/0xc8 [ 168.567536] el0_svc_common+0xc8/0x320 [ 168.567540] el0_svc_handler+0xf8/0x160 [ 168.567544] el0_svc+0x10/0x218 KASAN stacktrace: [ 168.567561] BUG: KASAN: null-ptr-deref in virtio_gpu_conn_get_modes+0xb4/0x140 [virtio_gpu] [ 168.567565] Read of size 4 at addr 0000000000000054 by task syz/6425 [ 168.567566] [ 168.567571] CPU: 1 PID: 6425 Comm: syz Kdump: loaded Not tainted 4.19.90-vhulk2201.1.0.h1035.kasan.eulerosv2r10.aarch64 #1 [ 168.567573] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 [ 168.567575] Call trace: [ 168.567578] dump_backtrace+0x0/0x310 [ 168.567582] show_stack+0x28/0x38 [ 168.567586] dump_stack+0xec/0x15c [ 168.567591] kasan_report+0x244/0x2f0 [ 168.567594] __asan_load4+0x58/0xb0 [ 168.567607] virtio_gpu_conn_get_modes+0xb4/0x140 [virtio_gpu] [ 168.567612] drm_helper_probe_single_connector_modes+0x3a4/0xd80 [ 168.567617] drm_mode_getconnector+0x2e0/0xa70 [ 168.567621] drm_ioctl_kernel+0x11c/0x1d8 [ 168.567624] drm_ioctl+0x558/0x6d0 [ 168.567628] do_vfs_ioctl+0x160/0xf30 [ 168.567632] ksys_ioctl+0x98/0xd8 [ 168.567636] __arm64_sys_ioctl+0x50/0xc8 [ 168.567641] el0_svc_common+0xc8/0x320 [ 168.567645] el0_svc_handler+0xf8/0x160 [ 168.567649] el0_svc+0x10/0x218
In the Linux kernel, the following vulnerability has been resolved: net: dsa: felix: fix possible NULL pointer dereference As the possible failure of the allocation, kzalloc() may return NULL pointer. Therefore, it should be better to check the 'sgi' in order to prevent the dereference of NULL pointer.
In the Linux kernel, the following vulnerability has been resolved: drm/msm/dpu: invalid parameter check in dpu_setup_dspp_pcc The function performs a check on the "ctx" input parameter, however, it is used before the check. Initialize the "base" variable after the sanity check to avoid a possible NULL pointer dereference. Addresses-Coverity-ID: 1493866 ("Null pointer dereference")
In the Linux kernel, the following vulnerability has been resolved: mtd: rawnand: cadence: fix possible null-ptr-deref in cadence_nand_dt_probe() It will cause null-ptr-deref when using 'res', if platform_get_resource() returns NULL, so move using 'res' after devm_ioremap_resource() that will check it to avoid null-ptr-deref. And use devm_platform_get_and_ioremap_resource() to simplify code.
In the Linux kernel, the following vulnerability has been resolved: hwmon: (asus-ec-sensors) Add checks for devm_kcalloc As the devm_kcalloc may return NULL, the return value needs to be checked to avoid NULL poineter dereference.