ghsa-qvwj-r2mj-jh93
Vulnerability from github
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
{
"affected": [],
"aliases": [
"CVE-2024-47689"
],
"database_specific": {
"cwe_ids": [
"CWE-362"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-10-21T12:15:05Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix to don\u0027t set SB_RDONLY in f2fs_handle_critical_error()\n\nsyzbot reports a f2fs bug as below:\n\n------------[ cut here ]------------\nWARNING: CPU: 1 PID: 58 at kernel/rcu/sync.c:177 rcu_sync_dtor+0xcd/0x180 kernel/rcu/sync.c:177\nCPU: 1 UID: 0 PID: 58 Comm: kworker/1:2 Not tainted 6.10.0-syzkaller-12562-g1722389b0d86 #0\nWorkqueue: events destroy_super_work\nRIP: 0010:rcu_sync_dtor+0xcd/0x180 kernel/rcu/sync.c:177\nCall Trace:\n percpu_free_rwsem+0x41/0x80 kernel/locking/percpu-rwsem.c:42\n destroy_super_work+0xec/0x130 fs/super.c:282\n process_one_work kernel/workqueue.c:3231 [inline]\n process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312\n worker_thread+0x86d/0xd40 kernel/workqueue.c:3390\n kthread+0x2f0/0x390 kernel/kthread.c:389\n ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n\nAs Christian Brauner pointed out [1]: the root cause is f2fs sets\nSB_RDONLY flag in internal function, rather than setting the flag\ncovered w/ sb-\u003es_umount semaphore via remount procedure, then below\nrace condition causes this bug:\n\n- freeze_super()\n - sb_wait_write(sb, SB_FREEZE_WRITE)\n - sb_wait_write(sb, SB_FREEZE_PAGEFAULT)\n - sb_wait_write(sb, SB_FREEZE_FS)\n\t\t\t\t\t- f2fs_handle_critical_error\n\t\t\t\t\t - sb-\u003es_flags |= SB_RDONLY\n- thaw_super\n - thaw_super_locked\n - sb_rdonly() is true, so it skips\n sb_freeze_unlock(sb, SB_FREEZE_FS)\n - deactivate_locked_super\n\nSince f2fs has almost the same logic as ext4 [2] when handling critical\nerror in filesystem if it mounts w/ errors=remount-ro option:\n- set CP_ERROR_FLAG flag which indicates filesystem is stopped\n- record errors to superblock\n- set SB_RDONLY falg\nOnce we set CP_ERROR_FLAG flag, all writable interfaces can detect the\nflag and stop any further updates on filesystem. So, it is safe to not\nset SB_RDONLY flag, let\u0027s remove the logic and keep in line w/ ext4 [3].\n\n[1] https://lore.kernel.org/all/20240729-himbeeren-funknetz-96e62f9c7aee@brauner\n[2] https://lore.kernel.org/all/20240729132721.hxih6ehigadqf7wx@quack3\n[3] https://lore.kernel.org/linux-ext4/20240805201241.27286-1-jack@suse.cz",
"id": "GHSA-qvwj-r2mj-jh93",
"modified": "2024-10-23T18:33:07Z",
"published": "2024-10-21T12:30:55Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-47689"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1f63f405c1a1a64b9c310388aad7055fb86b245c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/649ec8b30df113042588bd3d3cd4e98bcb1091e0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/930c6ab93492c4b15436524e704950b364b2930c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/de43021c72993877a8f86f9fddfa0687609da5a4"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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