In the Linux kernel 4.19 through 5.6.7 on the s390 platform, code execution may occur because of a race condition, as demonstrated by code in enable_sacf_uaccess in arch/s390/lib/uaccess.c that fails to protect against a concurrent page table upgrade, aka CID-3f777e19d171. A crash could also occur.

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in SMB request handling A race condition exists between SMB request handling in `ksmbd_conn_handler_loop()` and the freeing of `ksmbd_conn` in the workqueue handler `handle_ksmbd_work()`. This leads to a UAF. - KASAN: slab-use-after-free Read in handle_ksmbd_work - KASAN: slab-use-after-free in rtlock_slowlock_locked This race condition arises as follows: - `ksmbd_conn_handler_loop()` waits for `conn->r_count` to reach zero: `wait_event(conn->r_count_q, atomic_read(&conn->r_count) == 0);` - Meanwhile, `handle_ksmbd_work()` decrements `conn->r_count` using `atomic_dec_return(&conn->r_count)`, and if it reaches zero, calls `ksmbd_conn_free()`, which frees `conn`. - However, after `handle_ksmbd_work()` decrements `conn->r_count`, it may still access `conn->r_count_q` in the following line: `waitqueue_active(&conn->r_count_q)` or `wake_up(&conn->r_count_q)` This results in a UAF, as `conn` has already been freed. The discovery of this UAF can be referenced in the following PR for syzkaller's support for SMB requests.

A race condition in Linux kernel SCTP sockets (net/sctp/socket.c) before 5.12-rc8 can lead to kernel privilege escalation from the context of a network service or an unprivileged process. If sctp_destroy_sock is called without sock_net(sk)->sctp.addr_wq_lock then an element is removed from the auto_asconf_splist list without any proper locking. This can be exploited by an attacker with network service privileges to escalate to root or from the context of an unprivileged user directly if a BPF_CGROUP_INET_SOCK_CREATE is attached which denies creation of some SCTP socket.

The Linux Kernel versions 2.6.38 through 4.14 have a problematic use of pmd_mkdirty() in the touch_pmd() function inside the THP implementation. touch_pmd() can be reached by get_user_pages(). In such case, the pmd will become dirty. This scenario breaks the new can_follow_write_pmd()'s logic - pmd can become dirty without going through a COW cycle. This bug is not as severe as the original "Dirty cow" because an ext4 file (or any other regular file) cannot be mapped using THP. Nevertheless, it does allow us to overwrite read-only huge pages. For example, the zero huge page and sealed shmem files can be overwritten (since their mapping can be populated using THP). Note that after the first write page-fault to the zero page, it will be replaced with a new fresh (and zeroed) thp.

Linux kernel: Exploitable memory corruption due to UFO to non-UFO path switch. When building a UFO packet with MSG_MORE __ip_append_data() calls ip_ufo_append_data() to append. However in between two send() calls, the append path can be switched from UFO to non-UFO one, which leads to a memory corruption. In case UFO packet lengths exceeds MTU, copy = maxfraglen - skb->len becomes negative on the non-UFO path and the branch to allocate new skb is taken. This triggers fragmentation and computation of fraggap = skb_prev->len - maxfraglen. Fraggap can exceed MTU, causing copy = datalen - transhdrlen - fraggap to become negative. Subsequently skb_copy_and_csum_bits() writes out-of-bounds. A similar issue is present in IPv6 code. The bug was introduced in e89e9cf539a2 ("[IPv4/IPv6]: UFO Scatter-gather approach") on Oct 18 2005.

In unix_scm_to_skb of af_unix.c, there is a possible use after free bug due to a race condition. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-196926917References: Upstream kernel

Race condition in the IPC object implementation in the Linux kernel through 4.2.3 allows local users to gain privileges by triggering an ipc_addid call that leads to uid and gid comparisons against uninitialized data, related to msg.c, shm.c, and util.c.

SQLiteODBC 0.9996, as packaged for certain Linux distributions as 0.9996-4, has a race condition leading to root privilege escalation because any user can replace a /tmp/sqliteodbc$$ file with new contents that cause loading of an arbitrary library.

In the Linux kernel, the following vulnerability has been resolved: mm/mremap: fix move_normal_pmd/retract_page_tables race In mremap(), move_page_tables() looks at the type of the PMD entry and the specified address range to figure out by which method the next chunk of page table entries should be moved. At that point, the mmap_lock is held in write mode, but no rmap locks are held yet. For PMD entries that point to page tables and are fully covered by the source address range, move_pgt_entry(NORMAL_PMD, ...) is called, which first takes rmap locks, then does move_normal_pmd(). move_normal_pmd() takes the necessary page table locks at source and destination, then moves an entire page table from the source to the destination. The problem is: The rmap locks, which protect against concurrent page table removal by retract_page_tables() in the THP code, are only taken after the PMD entry has been read and it has been decided how to move it. So we can race as follows (with two processes that have mappings of the same tmpfs file that is stored on a tmpfs mount with huge=advise); note that process A accesses page tables through the MM while process B does it through the file rmap: process A process B ========= ========= mremap mremap_to move_vma move_page_tables get_old_pmd alloc_new_pmd *** PREEMPT *** madvise(MADV_COLLAPSE) do_madvise madvise_walk_vmas madvise_vma_behavior madvise_collapse hpage_collapse_scan_file collapse_file retract_page_tables i_mmap_lock_read(mapping) pmdp_collapse_flush i_mmap_unlock_read(mapping) move_pgt_entry(NORMAL_PMD, ...) take_rmap_locks move_normal_pmd drop_rmap_locks When this happens, move_normal_pmd() can end up creating bogus PMD entries in the line `pmd_populate(mm, new_pmd, pmd_pgtable(pmd))`. The effect depends on arch-specific and machine-specific details; on x86, you can end up with physical page 0 mapped as a page table, which is likely exploitable for user->kernel privilege escalation. Fix the race by letting process B recheck that the PMD still points to a page table after the rmap locks have been taken. Otherwise, we bail and let the caller fall back to the PTE-level copying path, which will then bail immediately at the pmd_none() check. Bug reachability: Reaching this bug requires that you can create shmem/file THP mappings - anonymous THP uses different code that doesn't zap stuff under rmap locks. File THP is gated on an experimental config flag (CONFIG_READ_ONLY_THP_FOR_FS), so on normal distro kernels you need shmem THP to hit this bug. As far as I know, getting shmem THP normally requires that you can mount your own tmpfs with the right mount flags, which would require creating your own user+mount namespace; though I don't know if some distros maybe enable shmem THP by default or something like that. Bug impact: This issue can likely be used for user->kernel privilege escalation when it is reachable.

In the Linux kernel, the following vulnerability has been resolved: media: venus: fix use after free bug in venus_remove due to race condition in venus_probe, core->work is bound with venus_sys_error_handler, which is used to handle error. The code use core->sys_err_done to make sync work. The core->work is started in venus_event_notify. If we call venus_remove, there might be an unfished work. The possible sequence is as follows: CPU0 CPU1 |venus_sys_error_handler venus_remove | hfi_destroy | venus_hfi_destroy | kfree(hdev); | |hfi_reinit |venus_hfi_queues_reinit |//use hdev Fix it by canceling the work in venus_remove.

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix race setting file private on concurrent lseek using same fd When doing concurrent lseek(2) system calls against the same file descriptor, using multiple threads belonging to the same process, we have a short time window where a race happens and can result in a memory leak. The race happens like this: 1) A program opens a file descriptor for a file and then spawns two threads (with the pthreads library for example), lets call them task A and task B; 2) Task A calls lseek with SEEK_DATA or SEEK_HOLE and ends up at file.c:find_desired_extent() while holding a read lock on the inode; 3) At the start of find_desired_extent(), it extracts the file's private_data pointer into a local variable named 'private', which has a value of NULL; 4) Task B also calls lseek with SEEK_DATA or SEEK_HOLE, locks the inode in shared mode and enters file.c:find_desired_extent(), where it also extracts file->private_data into its local variable 'private', which has a NULL value; 5) Because it saw a NULL file private, task A allocates a private structure and assigns to the file structure; 6) Task B also saw a NULL file private so it also allocates its own file private and then assigns it to the same file structure, since both tasks are using the same file descriptor. At this point we leak the private structure allocated by task A. Besides the memory leak, there's also the detail that both tasks end up using the same cached state record in the private structure (struct btrfs_file_private::llseek_cached_state), which can result in a use-after-free problem since one task can free it while the other is still using it (only one task took a reference count on it). Also, sharing the cached state is not a good idea since it could result in incorrect results in the future - right now it should not be a problem because it end ups being used only in extent-io-tree.c:count_range_bits() where we do range validation before using the cached state. Fix this by protecting the private assignment and check of a file while holding the inode's spinlock and keep track of the task that allocated the private, so that it's used only by that task in order to prevent user-after-free issues with the cached state record as well as potentially using it incorrectly in the future.

Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect handling of a copy-on-write (COW) feature to write to a read-only memory mapping, as exploited in the wild in October 2016, aka "Dirty COW."

Multiple race conditions in drivers/char/adsprpc.c and drivers/char/adsprpc_compat.c in the ADSPRPC driver for the Linux kernel 3.x, as used in Qualcomm Innovation Center (QuIC) Android contributions for MSM devices and other products, allow attackers to cause a denial of service (zero-value write) or possibly have unspecified other impact via a COMPAT_FASTRPC_IOCTL_INVOKE_FD ioctl call.

In the Linux kernel, the following vulnerability has been resolved: netfilter: ipset: Fix race between namespace cleanup and gc in the list:set type Lion Ackermann reported that there is a race condition between namespace cleanup in ipset and the garbage collection of the list:set type. The namespace cleanup can destroy the list:set type of sets while the gc of the set type is waiting to run in rcu cleanup. The latter uses data from the destroyed set which thus leads use after free. The patch contains the following parts: - When destroying all sets, first remove the garbage collectors, then wait if needed and then destroy the sets. - Fix the badly ordered "wait then remove gc" for the destroy a single set case. - Fix the missing rcu locking in the list:set type in the userspace test case. - Use proper RCU list handlings in the list:set type. The patch depends on c1193d9bbbd3 (netfilter: ipset: Add list flush to cancel_gc).

init_tmp in TeeJee.FileSystem.vala in Timeshift before 20.03 unsafely reuses a preexisting temporary directory in the predictable location /tmp/timeshift. It follows symlinks in this location or uses directories owned by unprivileged users. Because Timeshift also executes scripts under this location, an attacker can attempt to win a race condition to replace scripts created by Timeshift with attacker-controlled scripts. Upon success, an attacker-controlled script is executed with full root privileges. This logic is practically always triggered when Timeshift runs regardless of the command-line arguments used.

In the Linux kernel, the following vulnerability has been resolved: gpiolib: cdev: Fix use after free in lineinfo_changed_notify The use-after-free issue occurs as follows: when the GPIO chip device file is being closed by invoking gpio_chrdev_release(), watched_lines is freed by bitmap_free(), but the unregistration of lineinfo_changed_nb notifier chain failed due to waiting write rwsem. Additionally, one of the GPIO chip's lines is also in the release process and holds the notifier chain's read rwsem. Consequently, a race condition leads to the use-after-free of watched_lines. Here is the typical stack when issue happened: [free] gpio_chrdev_release() --> bitmap_free(cdev->watched_lines) <-- freed --> blocking_notifier_chain_unregister() --> down_write(&nh->rwsem) <-- waiting rwsem --> __down_write_common() --> rwsem_down_write_slowpath() --> schedule_preempt_disabled() --> schedule() [use] st54spi_gpio_dev_release() --> gpio_free() --> gpiod_free() --> gpiod_free_commit() --> gpiod_line_state_notify() --> blocking_notifier_call_chain() --> down_read(&nh->rwsem); <-- held rwsem --> notifier_call_chain() --> lineinfo_changed_notify() --> test_bit(xxxx, cdev->watched_lines) <-- use after free The side effect of the use-after-free issue is that a GPIO line event is being generated for userspace where it shouldn't. However, since the chrdev is being closed, userspace won't have the chance to read that event anyway. To fix the issue, call the bitmap_free() function after the unregistration of lineinfo_changed_nb notifier chain.

Integer signedness error in the btrfs_ioctl_space_info function in the Linux kernel 2.6.37 allows local users to cause a denial of service (heap-based buffer overflow) or possibly have unspecified other impact via a crafted slot value.

Race condition in NVMap in NVIDIA Tegra Linux Kernel 3.10 allows local users to gain privileges via a crafted NVMAP_IOC_CREATE IOCTL call, which triggers a use-after-free error, as demonstrated by using a race condition to escape the Chrome sandbox.

An issue was discovered in mm/mmap.c in the Linux kernel before 5.7.11. There is a race condition between certain expand functions (expand_downwards and expand_upwards) and page-table free operations from an munmap call, aka CID-246c320a8cfe.

An issue was discovered in kmem_cache_alloc_bulk in mm/slub.c in the Linux kernel before 5.5.11. The slowpath lacks the required TID increment, aka CID-fd4d9c7d0c71.

Race condition in the mounting process in vmware-mount in VMware Workstation 7.x before 7.1.2 build 301548 on Linux, VMware Player 3.1.x before 3.1.2 build 301548 on Linux, VMware Server 2.0.2 on Linux, and VMware Fusion 3.1.x before 3.1.2 build 332101 allows host OS users to gain privileges via vectors involving temporary files.

Race condition in the hvc_close function in drivers/char/hvc_console.c in the Linux kernel before 2.6.34 allows local users to cause a denial of service or possibly have unspecified other impact by closing a Hypervisor Virtual Console device, related to the hvc_open and hvc_remove functions.

deepin-clone before 1.1.3 uses a predictable path /tmp/.deepin-clone/mount/<block-dev-basename> in the Helper::temporaryMountDevice() function to temporarily mount a file system as root. An unprivileged user can prepare a symlink at this location to have the file system mounted in an arbitrary location. By winning a race condition, the attacker can also enter the mount point, thereby preventing a subsequent unmount of the file system.

An issue was discovered in drivers/media/platform/vivid in the Linux kernel through 5.3.8. It is exploitable for privilege escalation on some Linux distributions where local users have /dev/video0 access, but only if the driver happens to be loaded. There are multiple race conditions during streaming stopping in this driver (part of the V4L2 subsystem). These issues are caused by wrong mutex locking in vivid_stop_generating_vid_cap(), vivid_stop_generating_vid_out(), sdr_cap_stop_streaming(), and the corresponding kthreads. At least one of these race conditions leads to a use-after-free.

A use-after-free flaw was found in the Linux kernel’s sound subsystem in the way a user triggers concurrent calls of PCM hw_params. The hw_free ioctls or similar race condition happens inside ALSA PCM for other ioctls. This flaw allows a local user to crash or potentially escalate their privileges on the system.

A race condition was found the Linux kernel in perf_event_open() which can be exploited by an unprivileged user to gain root privileges. The bug allows to build several exploit primitives such as kernel address information leak, arbitrary execution, etc.

Race condition in the find_keyring_by_name function in security/keys/keyring.c in the Linux kernel 2.6.34-rc5 and earlier allows local users to cause a denial of service (memory corruption and system crash) or possibly have unspecified other impact via keyctl session commands that trigger access to a dead keyring that is undergoing deletion by the key_cleanup function.

The fix for CVE-2019-11599, affecting the Linux kernel before 5.0.10 was not complete. A local user could use this flaw to obtain sensitive information, cause a denial of service, or possibly have other unspecified impacts by triggering a race condition with mmget_not_zero or get_task_mm calls.

Race condition in the ptrace_attach function in kernel/ptrace.c in the Linux kernel before 2.6.30-rc4 allows local users to gain privileges via a PTRACE_ATTACH ptrace call during an exec system call that is launching a setuid application, related to locking an incorrect cred_exec_mutex object.

In the Linux kernel, the following vulnerability has been resolved: riscv: fix race when vmap stack overflow Currently, when detecting vmap stack overflow, riscv firstly switches to the so called shadow stack, then use this shadow stack to call the get_overflow_stack() to get the overflow stack. However, there's a race here if two or more harts use the same shadow stack at the same time. To solve this race, we introduce spin_shadow_stack atomic var, which will be swap between its own address and 0 in atomic way, when the var is set, it means the shadow_stack is being used; when the var is cleared, it means the shadow_stack isn't being used. [Palmer: Add AQ to the swap, and also some comments.]

It was discovered freeradius up to and including version 3.0.19 does not correctly configure logrotate, allowing a local attacker who already has control of the radiusd user to escalate his privileges to root, by tricking logrotate into writing a radiusd-writable file to a directory normally inaccessible by the radiusd user. NOTE: the upstream software maintainer has stated "there is simply no way for anyone to gain privileges through this alleged issue."

Race condition in the ALSA subsystem in the Linux kernel before 4.13.8 allows local users to cause a denial of service (use-after-free) or possibly have unspecified other impact via crafted /dev/snd/seq ioctl calls, related to sound/core/seq/seq_clientmgr.c and sound/core/seq/seq_ports.c.

An issue was discovered in the __ns_get_path function in fs/nsfs.c in the Linux kernel before 4.11. Due to a race condition when accessing files, a Use After Free condition can occur. This also affects all Android releases from CAF using the Linux kernel (Android for MSM, Firefox OS for MSM, QRD Android) before security patch level 2018-07-05.

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: Fix potential data-race in __nft_expr_type_get() nft_unregister_expr() can concurrent with __nft_expr_type_get(), and there is not any protection when iterate over nf_tables_expressions list in __nft_expr_type_get(). Therefore, there is potential data-race of nf_tables_expressions list entry. Use list_for_each_entry_rcu() to iterate over nf_tables_expressions list in __nft_expr_type_get(), and use rcu_read_lock() in the caller nft_expr_type_get() to protect the entire type query process.

An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded.

The Siemens R3964 line discipline driver in drivers/tty/n_r3964.c in the Linux kernel before 5.0.8 has multiple race conditions.

SchedMD Slurm 23.02.x before 23.02.6 and 22.05.x before 22.05.10 allows filesystem race conditions for gaining ownership of a file, overwriting a file, or deleting files.

Race condition in the L2TPv3 IP Encapsulation feature in the Linux kernel before 4.8.14 allows local users to gain privileges or cause a denial of service (use-after-free) by making multiple bind system calls without properly ascertaining whether a socket has the SOCK_ZAPPED status, related to net/l2tp/l2tp_ip.c and net/l2tp/l2tp_ip6.c.

An issue was discovered in the Linux kernel before 6.3.2. A use-after-free was found in dm1105_remove in drivers/media/pci/dm1105/dm1105.c.

An issue was discovered in the Linux kernel before 6.3.2. A use-after-free was found in cedrus_remove in drivers/staging/media/sunxi/cedrus/cedrus.c.

An issue was discovered in the Linux kernel before 6.3.2. A use-after-free was found in saa7134_finidev in drivers/media/pci/saa7134/saa7134-core.c.

An issue was discovered in the Linux kernel before 6.3.2. A use-after-free was found in rkvdec_remove in drivers/staging/media/rkvdec/rkvdec.c.

An issue was discovered in the Linux kernel before 6.3.2. A use-after-free was found in renesas_usb3_remove in drivers/usb/gadget/udc/renesas_usb3.c.

Race condition in the pkexec utility and polkitd daemon in PolicyKit (aka polkit) 0.96 allows local users to gain privileges by executing a setuid program from pkexec, related to the use of the effective user ID instead of the real user ID.

A race condition occurred between the functions lmLogClose and txEnd in JFS, in the Linux Kernel, executed in different threads. This flaw allows a local attacker with normal user privileges to crash the system or leak internal kernel information.

In the Linux kernel, the following vulnerability has been resolved: fs/proc/task_mmu: move mmu notification mechanism inside mm lock Move mmu notification mechanism inside mm lock to prevent race condition in other components which depend on it. The notifier will invalidate memory range. Depending upon the number of iterations, different memory ranges would be invalidated. The following warning would be removed by this patch: WARNING: CPU: 0 PID: 5067 at arch/x86/kvm/../../../virt/kvm/kvm_main.c:734 kvm_mmu_notifier_change_pte+0x860/0x960 arch/x86/kvm/../../../virt/kvm/kvm_main.c:734 There is no behavioural and performance change with this patch when there is no component registered with the mmu notifier. [akpm@linux-foundation.org: narrow the scope of `range', per Sean]

In the Linux kernel, the following vulnerability has been resolved: net: phylink: add lock for serializing concurrent pl->phydev writes with resolver Currently phylink_resolve() protects itself against concurrent phylink_bringup_phy() or phylink_disconnect_phy() calls which modify pl->phydev by relying on pl->state_mutex. The problem is that in phylink_resolve(), pl->state_mutex is in a lock inversion state with pl->phydev->lock. So pl->phydev->lock needs to be acquired prior to pl->state_mutex. But that requires dereferencing pl->phydev in the first place, and without pl->state_mutex, that is racy. Hence the reason for the extra lock. Currently it is redundant, but it will serve a functional purpose once mutex_lock(&phy->lock) will be moved outside of the mutex_lock(&pl->state_mutex) section. Another alternative considered would have been to let phylink_resolve() acquire the rtnl_mutex, which is also held when phylink_bringup_phy() and phylink_disconnect_phy() are called. But since phylink_disconnect_phy() runs under rtnl_lock(), it would deadlock with phylink_resolve() when calling flush_work(&pl->resolve). Additionally, it would have been undesirable because it would have unnecessarily blocked many other call paths as well in the entire kernel, so the smaller-scoped lock was preferred.