| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-47689: f2fs: fix to don't set SB_RDONLY in f2fs_handle_critical_error() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| f2fs: fix to don't set SB_RDONLY in f2fs_handle_critical_error() |
| |
| syzbot reports a f2fs bug as below: |
| |
| ------------[ cut here ]------------ |
| WARNING: CPU: 1 PID: 58 at kernel/rcu/sync.c:177 rcu_sync_dtor+0xcd/0x180 kernel/rcu/sync.c:177 |
| CPU: 1 UID: 0 PID: 58 Comm: kworker/1:2 Not tainted 6.10.0-syzkaller-12562-g1722389b0d86 #0 |
| Workqueue: events destroy_super_work |
| RIP: 0010:rcu_sync_dtor+0xcd/0x180 kernel/rcu/sync.c:177 |
| Call Trace: |
| percpu_free_rwsem+0x41/0x80 kernel/locking/percpu-rwsem.c:42 |
| destroy_super_work+0xec/0x130 fs/super.c:282 |
| process_one_work kernel/workqueue.c:3231 [inline] |
| process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312 |
| worker_thread+0x86d/0xd40 kernel/workqueue.c:3390 |
| kthread+0x2f0/0x390 kernel/kthread.c:389 |
| ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 |
| ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 |
| |
| As Christian Brauner pointed out [1]: the root cause is f2fs sets |
| SB_RDONLY flag in internal function, rather than setting the flag |
| covered w/ sb->s_umount semaphore via remount procedure, then below |
| race condition causes this bug: |
| |
| - freeze_super() |
| - sb_wait_write(sb, SB_FREEZE_WRITE) |
| - sb_wait_write(sb, SB_FREEZE_PAGEFAULT) |
| - sb_wait_write(sb, SB_FREEZE_FS) |
| - f2fs_handle_critical_error |
| - sb->s_flags |= SB_RDONLY |
| - thaw_super |
| - thaw_super_locked |
| - sb_rdonly() is true, so it skips |
| sb_freeze_unlock(sb, SB_FREEZE_FS) |
| - deactivate_locked_super |
| |
| Since f2fs has almost the same logic as ext4 [2] when handling critical |
| error in filesystem if it mounts w/ errors=remount-ro option: |
| - set CP_ERROR_FLAG flag which indicates filesystem is stopped |
| - record errors to superblock |
| - set SB_RDONLY falg |
| Once we set CP_ERROR_FLAG flag, all writable interfaces can detect the |
| flag and stop any further updates on filesystem. So, it is safe to not |
| set SB_RDONLY flag, let's remove the logic and keep in line w/ ext4 [3]. |
| |
| [1] https://lore.kernel.org/all/20240729-himbeeren-funknetz-96e62f9c7aee@brauner |
| [2] https://lore.kernel.org/all/20240729132721.hxih6ehigadqf7wx@quack3 |
| [3] https://lore.kernel.org/linux-ext4/20240805201241.27286-1-jack@suse.cz |
| |
| The Linux kernel CVE team has assigned CVE-2024-47689 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.5 with commit b62e71be2110d8b52bf5faf3c3ed7ca1a0c113a5 and fixed in 6.6.54 with commit 649ec8b30df113042588bd3d3cd4e98bcb1091e0 |
| Issue introduced in 6.5 with commit b62e71be2110d8b52bf5faf3c3ed7ca1a0c113a5 and fixed in 6.10.13 with commit de43021c72993877a8f86f9fddfa0687609da5a4 |
| Issue introduced in 6.5 with commit b62e71be2110d8b52bf5faf3c3ed7ca1a0c113a5 and fixed in 6.11.2 with commit 1f63f405c1a1a64b9c310388aad7055fb86b245c |
| Issue introduced in 6.5 with commit b62e71be2110d8b52bf5faf3c3ed7ca1a0c113a5 and fixed in 6.12 with commit 930c6ab93492c4b15436524e704950b364b2930c |
| Issue introduced in 6.4.4 with commit ed1d478bf838820201f3fb67a1748fdf15954ea4 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-47689 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| fs/f2fs/super.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/649ec8b30df113042588bd3d3cd4e98bcb1091e0 |
| https://git.kernel.org/stable/c/de43021c72993877a8f86f9fddfa0687609da5a4 |
| https://git.kernel.org/stable/c/1f63f405c1a1a64b9c310388aad7055fb86b245c |
| https://git.kernel.org/stable/c/930c6ab93492c4b15436524e704950b364b2930c |
