Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix race between cache write completion and ALL_QUEUED being set When netfslib is issuing subrequests, the subrequests start processing immediately and may complete before we reach the end of the issuing function. At the end of the issuing function we set NETFS_RREQ_ALL_QUEUED to indicate to the collector that we aren't going to issue any more subreqs and that it can do the final notifications and cleanup. Now, this isn't a problem if the request is synchronous (NETFS_RREQ_OFFLOAD_COLLECTION is unset) as the result collection will be done in-thread and we're guaranteed an opportunity to run the collector. However, if the request is asynchronous, collection is primarily triggered by the termination of subrequests queuing it on a workqueue. Now, a race can occur here if the app thread sets ALL_QUEUED after the last subrequest terminates. This can happen most easily with the copy2cache code (as used by Ceph) where, in the collection routine of a read request, an asynchronous write request is spawned to copy data to the cache. Folios are added to the write request as they're unlocked, but there may be a delay before ALL_QUEUED is set as the write subrequests may complete before we get there. If all the write subreqs have finished by the ALL_QUEUED point, no further events happen and the collection never happens, leaving the request hanging. Fix this by queuing the collector after setting ALL_QUEUED. This is a bit heavy-handed and it may be sufficient to do it only if there are no extant subreqs. Also add a tracepoint to cross-reference both requests in a copy-to-request operation and add a trace to the netfs_rreq tracepoint to indicate the setting of ALL_QUEUED.Show less

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_qfq: Fix race condition on qfq_aggregate A race condition can occur when 'agg' is modified in qfq_change_agg (called during qfq_enqueue) while other threads access it concurrently. For example, qfq_dump_class may trigger a NULL dereference, and qfq_delete_class may cause a use-after-free. This patch addresses the issue by: 1. Moved qfq_destroy_class into the critical section. 2. Added sch_tree_lock protection to qfq_dump_class and qfq_dump_class_stats.Show less

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: u_serial: Fix race condition in TTY wakeup A race condition occurs when gs_start_io() calls either gs_start_rx() or gs_start_tx(), as those functions briefly drop the port_lock for usb_ep_queue(). This allows gs_close() and gserial_disconnect() to clear port.tty and port_usb, respectively. Use the null-safe TTY Port helper function to wake up TTY. Example CPU1: CPU2: gserial_connect() // lock gs_close() // await lock gs_start_rx() // unlock usb_ep_queue() gs_close() // lock, reset port.tty and unlock gs_start_rx() // lock tty_wakeup() // NPEShow less

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: Fix race between DIM disable and net_dim() There's a race between disabling DIM and NAPI callbacks using the dim pointer on the RQ or SQ. If NAPI checks the DIM state bit and sees it still set, it assumes `rq->dim` or `sq->dim` is valid. But if DIM gets disabled right after that check, the pointer might already be set to NULL, leading to a NULL pointer dereference in net_dim(). Fix this by calling `synchronize_net()` before freeing the DIM context. This ensures all in-progress NAPI callbacks are finished before the pointer is cleared. Kernel log: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... RIP: 0010:net_dim+0x23/0x190 ... Call Trace: <TASK> ? __die+0x20/0x60 ? page_fault_oops+0x150/0x3e0 ? common_interrupt+0xf/0xa0 ? sysvec_call_function_single+0xb/0x90 ? exc_page_fault+0x74/0x130 ? asm_exc_page_fault+0x22/0x30 ? net_dim+0x23/0x190 ? mlx5e_poll_ico_cq+0x41/0x6f0 [mlx5_core] ? sysvec_apic_timer_interrupt+0xb/0x90 mlx5e_handle_rx_dim+0x92/0xd0 [mlx5_core] mlx5e_napi_poll+0x2cd/0xac0 [mlx5_core] ? mlx5e_poll_ico_cq+0xe5/0x6f0 [mlx5_core] busy_poll_stop+0xa2/0x200 ? mlx5e_napi_poll+0x1d9/0xac0 [mlx5_core] ? mlx5e_trigger_irq+0x130/0x130 [mlx5_core] __napi_busy_loop+0x345/0x3b0 ? sysvec_call_function_single+0xb/0x90 ? asm_sysvec_call_function_single+0x16/0x20 ? sysvec_apic_timer_interrupt+0xb/0x90 ? pcpu_free_area+0x1e4/0x2e0 napi_busy_loop+0x11/0x20 xsk_recvmsg+0x10c/0x130 sock_recvmsg+0x44/0x70 __sys_recvfrom+0xbc/0x130 ? __schedule+0x398/0x890 __x64_sys_recvfrom+0x20/0x30 do_syscall_64+0x4c/0x100 entry_SYSCALL_64_after_hwframe+0x4b/0x53 ... ---[ end trace 0000000000000000 ]--- ... ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---Show less

In the Linux kernel, the following vulnerability has been resolved: NFSv4/pNFS: Fix a race to wake on NFS_LAYOUT_DRAIN We found a few different systems hung up in writeback waiting on the same page lock, and one task waiting on the NFS_LAYOUT_DRAIN bit in pnfs_update_layout(), however the pnfs_layout_hdr's plh_outstanding count was zero. It seems most likely that this is another race between the waiter and waker similar to commit ed0172af5d6f ("SUNRPC: Fix a race to wake a sync task"). Fix it up by applying the advised barrier.Show less

In the Linux kernel, the following vulnerability has been resolved: mm/vmalloc: fix data race in show_numa_info() The following data-race was found in show_numa_info(): ================================================================== BUG: KCSAN: data-race in vmalloc_info_show / vmalloc_info_show read to 0xffff88800971fe30 of 4 bytes by task 8289 on cpu 0: show_numa_info mm/vmalloc.c:4936 [inline] vmalloc_info_show+0x5a8/0x7e0 mm/vmalloc.c:5016 seq_read_iter+0x373/0xb40 fs/seq_file.c:230 proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299 .... write to 0xffff88800971fe30 of 4 bytes by task 8287 on cpu 1: show_numa_info mm/vmalloc.c:4934 [inline] vmalloc_info_show+0x38f/0x7e0 mm/vmalloc.c:5016 seq_read_iter+0x373/0xb40 fs/seq_file.c:230 proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299 .... value changed: 0x0000008f -> 0x00000000 ================================================================== According to this report,there is a read/write data-race because m->private is accessible to multiple CPUs. To fix this, instead of allocating the heap in proc_vmalloc_init() and passing the heap address to m->private, vmalloc_info_show() should allocate the heap.Show less

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix a race between renames and directory logging We have a race between a rename and directory inode logging that if it happens and we crash/power fail before the rename completes, the next time the filesystem is mounted, the log replay code will end up deleting the file that was being renamed. This is best explained following a step by step analysis of an interleaving of steps that lead into this situation. Consider the initial conditions: 1) We are at transaction N; 2) We have directories A and B created in a past transaction (< N); 3) We have inode X corresponding to a file that has 2 hardlinks, one in directory A and the other in directory B, so we'll name them as "A/foo_link1" and "B/foo_link2". Both hard links were persisted in a past transaction (< N); 4) We have inode Y corresponding to a file that as a single hard link and is located in directory A, we'll name it as "A/bar". This file was also persisted in a past transaction (< N). The steps leading to a file loss are the following and for all of them we are under transaction N: 1) Link "A/foo_link1" is removed, so inode's X last_unlink_trans field is updated to N, through btrfs_unlink() -> btrfs_record_unlink_dir(); 2) Task A starts a rename for inode Y, with the goal of renaming from "A/bar" to "A/baz", so we enter btrfs_rename(); 3) Task A inserts the new BTRFS_INODE_REF_KEY for inode Y by calling btrfs_insert_inode_ref(); 4) Because the rename happens in the same directory, we don't set the last_unlink_trans field of directoty A's inode to the current transaction id, that is, we don't cal btrfs_record_unlink_dir(); 5) Task A then removes the entries from directory A (BTRFS_DIR_ITEM_KEY and BTRFS_DIR_INDEX_KEY items) when calling __btrfs_unlink_inode() (actually the dir index item is added as a delayed item, but the effect is the same); 6) Now before task A adds the new entry "A/baz" to directory A by calling btrfs_add_link(), another task, task B is logging inode X; 7) Task B starts a fsync of inode X and after logging inode X, at btrfs_log_inode_parent() it calls btrfs_log_all_parents(), since inode X has a last_unlink_trans value of N, set at in step 1; 8) At btrfs_log_all_parents() we search for all parent directories of inode X using the commit root, so we find directories A and B and log them. Bu when logging direct A, we don't have a dir index item for inode Y anymore, neither the old name "A/bar" nor for the new name "A/baz" since the rename has deleted the old name but has not yet inserted the new name - task A hasn't called yet btrfs_add_link() to do that. Note that logging directory A doesn't fallback to a transaction commit because its last_unlink_trans has a lower value than the current transaction's id (see step 4); 9) Task B finishes logging directories A and B and gets back to btrfs_sync_file() where it calls btrfs_sync_log() to persist the log tree; 10) Task B successfully persisted the log tree, btrfs_sync_log() completed with success, and a power failure happened. We have a log tree without any directory entry for inode Y, so the log replay code deletes the entry for inode Y, name "A/bar", from the subvolume tree since it doesn't exist in the log tree and the log tree is authorative for its index (we logged a BTRFS_DIR_LOG_INDEX_KEY item that covers the index range for the dentry that corresponds to "A/bar"). Since there's no other hard link for inode Y and the log replay code deletes the name "A/bar", the file is lost. The issue wouldn't happen if task B synced the log only after task A called btrfs_log_new_name(), which would update the log with the new name for inode Y ("A/bar"). Fix this by pinning the log root during renames before removing the old directory entry, and unpinning af ---truncated---Show less

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix race between async reclaim worker and close_ctree() Syzbot reported an assertion failure due to an attempt to add a delayed iput after we have set BTRFS_FS_STATE_NO_DELAYED_IPUT in the fs_info state: WARNING: CPU: 0 PID: 65 at fs/btrfs/inode.c:3420 btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420 Modules linked in: CPU: 0 UID: 0 PID: 65 Comm: kworker/u8:4 Not tainted 6.15.0-next-20250530-syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: btrfs-endio-write btrfs_work_helper RIP: 0010:btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420 Code: 4e ad 5d (...) RSP: 0018:ffffc9000213f780 EFLAGS: 00010293 RAX: ffffffff83c635b7 RBX: ffff888058920000 RCX: ffff88801c769e00 RDX: 0000000000000000 RSI: 0000000000000100 RDI: 0000000000000000 RBP: 0000000000000001 R08: ffff888058921b67 R09: 1ffff1100b12436c R10: dffffc0000000000 R11: ffffed100b12436d R12: 0000000000000001 R13: dffffc0000000000 R14: ffff88807d748000 R15: 0000000000000100 FS: 0000000000000000(0000) GS:ffff888125c53000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00002000000bd038 CR3: 000000006a142000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> btrfs_put_ordered_extent+0x19f/0x470 fs/btrfs/ordered-data.c:635 btrfs_finish_one_ordered+0x11d8/0x1b10 fs/btrfs/inode.c:3312 btrfs_work_helper+0x399/0xc20 fs/btrfs/async-thread.c:312 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> This can happen due to a race with the async reclaim worker like this: 1) The async metadata reclaim worker enters shrink_delalloc(), which calls btrfs_start_delalloc_roots() with an nr_pages argument that has a value less than LONG_MAX, and that in turn enters start_delalloc_inodes(), which sets the local variable 'full_flush' to false because wbc->nr_to_write is less than LONG_MAX; 2) There it finds inode X in a root's delalloc list, grabs a reference for inode X (with igrab()), and triggers writeback for it with filemap_fdatawrite_wbc(), which creates an ordered extent for inode X; 3) The unmount sequence starts from another task, we enter close_ctree() and we flush the workqueue fs_info->endio_write_workers, which waits for the ordered extent for inode X to complete and when dropping the last reference of the ordered extent, with btrfs_put_ordered_extent(), when we call btrfs_add_delayed_iput() we don't add the inode to the list of delayed iputs because it has a refcount of 2, so we decrement it to 1 and return; 4) Shortly after at close_ctree() we call btrfs_run_delayed_iputs() which runs all delayed iputs, and then we set BTRFS_FS_STATE_NO_DELAYED_IPUT in the fs_info state; 5) The async reclaim worker, after calling filemap_fdatawrite_wbc(), now calls btrfs_add_delayed_iput() for inode X and there we trigger an assertion failure since the fs_info state has the flag BTRFS_FS_STATE_NO_DELAYED_IPUT set. Fix this by setting BTRFS_FS_STATE_NO_DELAYED_IPUT only after we wait for the async reclaim workers to finish, after we call cancel_work_sync() for them at close_ctree(), and by running delayed iputs after wait for the reclaim workers to finish and before setting the bit. This race was recently introduced by commit 19e60b2a95f5 ("btrfs: add extra warning if delayed iput is added when it's not allowed"). Without the new validation at btrfs_add_delayed_iput(), ---truncated---Show less

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in Apache Tomcat when using the APR/Native connector. This was particularly noticeable with client initiated closes of HTTP/2 connections. This issue affects Apache Tomcat: from 9.0.0.M1 through 9.0.106. The following versions were EOL at the time the CVE was created but are known to be affected: 8.5.0 through 8.5.100. Other, older, EOL versions may also be affected. Users are recommended to upgrade to version 9.0.107, which fixes the issue.Show less

In the Linux kernel, the following vulnerability has been resolved: fs/fhandle.c: fix a race in call of has_locked_children() may_decode_fh() is calling has_locked_children() while holding no locks. That's an oopsable race... The rest of the callers are safe since they are holding namespace_sem and are guaranteed a positive refcount on the mount in question. Rename the current has_locked_children() to __has_locked_children(), make it static and switch the fs/namespace.c users to it. Make has_locked_children() a wrapper for __has_locked_children(), calling the latter under read_seqlock_excl(&mount_lock).Show less

In the Linux kernel, the following vulnerability has been resolved: wifi: ath12k: fix node corruption in ar->arvifs list In current WLAN recovery code flow, ath12k_core_halt() only reinitializes the "arvifs" list head. This will cause the list node immediately following the list head to become an invalid list node. Because the prev of that node still points to the list head "arvifs", but the next of the list head "arvifs" no longer points to that list node. When a WLAN recovery occurs during the execution of a vif removal, and it happens before the spin_lock_bh(&ar->data_lock) in ath12k_mac_vdev_delete(), list_del() will detect the previously mentioned situation, thereby triggering a kernel panic. The fix is to remove and reinitialize all vif list nodes from the list head "arvifs" during WLAN halt. The reinitialization is to make the list nodes valid, ensuring that the list_del() in ath12k_mac_vdev_delete() can execute normally. Call trace: __list_del_entry_valid_or_report+0xd4/0x100 (P) ath12k_mac_remove_link_interface.isra.0+0xf8/0x2e4 [ath12k] ath12k_scan_vdev_clean_work+0x40/0x164 [ath12k] cfg80211_wiphy_work+0xfc/0x100 process_one_work+0x164/0x2d0 worker_thread+0x254/0x380 kthread+0xfc/0x100 ret_from_fork+0x10/0x20 The change is mostly copied from the ath11k patch: https://lore.kernel.org/all/20250320053145.3445187-1-quic_stonez@quicinc.com/ Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.4.1-00199-QCAHKSWPL_SILICONZ-1Show less

In the Linux kernel, the following vulnerability has been resolved: mm: userfaultfd: fix race of userfaultfd_move and swap cache This commit fixes two kinds of races, they may have different results: Barry reported a BUG_ON in commit c50f8e6053b0, we may see the same BUG_ON if the filemap lookup returned NULL and folio is added to swap cache after that. If another kind of race is triggered (folio changed after lookup) we may see RSS counter is corrupted: [ 406.893936] BUG: Bad rss-counter state mm:ffff0000c5a9ddc0 type:MM_ANONPAGES val:-1 [ 406.894071] BUG: Bad rss-counter state mm:ffff0000c5a9ddc0 type:MM_SHMEMPAGES val:1 Because the folio is being accounted to the wrong VMA. I'm not sure if there will be any data corruption though, seems no. The issues above are critical already. On seeing a swap entry PTE, userfaultfd_move does a lockless swap cache lookup, and tries to move the found folio to the faulting vma. Currently, it relies on checking the PTE value to ensure that the moved folio still belongs to the src swap entry and that no new folio has been added to the swap cache, which turns out to be unreliable. While working and reviewing the swap table series with Barry, following existing races are observed and reproduced [1]: In the example below, move_pages_pte is moving src_pte to dst_pte, where src_pte is a swap entry PTE holding swap entry S1, and S1 is not in the swap cache: CPU1 CPU2 userfaultfd_move move_pages_pte() entry = pte_to_swp_entry(orig_src_pte); // Here it got entry = S1 ... < interrupted> ... <swapin src_pte, alloc and use folio A> // folio A is a new allocated folio // and get installed into src_pte <frees swap entry S1> // src_pte now points to folio A, S1 // has swap count == 0, it can be freed // by folio_swap_swap or swap // allocator's reclaim. <try to swap out another folio B> // folio B is a folio in another VMA. <put folio B to swap cache using S1 > // S1 is freed, folio B can use it // for swap out with no problem. ... folio = filemap_get_folio(S1) // Got folio B here !!! ... < interrupted again> ... <swapin folio B and free S1> // Now S1 is free to be used again. <swapout src_pte & folio A using S1> // Now src_pte is a swap entry PTE // holding S1 again. folio_trylock(folio) move_swap_pte double_pt_lock is_pte_pages_stable // Check passed because src_pte == S1 folio_move_anon_rmap(...) // Moved invalid folio B here !!! The race window is very short and requires multiple collisions of multiple rare events, so it's very unlikely to happen, but with a deliberately constructed reproducer and increased time window, it can be reproduced easily. This can be fixed by checking if the folio returned by filemap is the valid swap cache folio after acquiring the folio lock. Another similar race is possible: filemap_get_folio may return NULL, but folio (A) could be swapped in and then swapped out again using the same swap entry after the lookup. In such a case, folio (A) may remain in the swap cache, so it must be moved too: CPU1 CPU2 userfaultfd_move move_pages_pte() entry = pte_to_swp_entry(orig_src_pte); // Here it got entry = S1, and S1 is not in swap cache folio = filemap_get ---truncated---Show less