Описание
In the Linux kernel, the following vulnerability has been resolved:
ext2: reject inodes with zero i_nlink and valid mode in ext2_iget()
ext2_iget() already rejects inodes with i_nlink == 0 when i_mode is
zero or i_dtime is set, treating them as deleted. However, the case of
i_nlink == 0 with a non-zero mode and zero dtime slips through. Since
ext2 has no orphan list, such a combination can only result from
filesystem corruption - a legitimate inode deletion always sets either
i_dtime or clears i_mode before freeing the inode.
A crafted image can exploit this gap to present such an inode to the
VFS, which then triggers WARN_ON inside drop_nlink() (fs/inode.c) via
ext2_unlink(), ext2_rename() and ext2_rmdir():
WARNING: CPU: 3 PID: 609 at fs/inode.c:336 drop_nlink+0xad/0xd0 fs/inode.c:336
CPU: 3 UID: 0 PID: 609 Comm: syz-executor Not tainted 6.12.77+ #1
Call Trace:
inode_dec_link_count include/linux/fs.h:2518 [inline]
ext2_unlink+0x26c/0x300 fs/ext2/namei.c:295
vfs_unlink+0x2fc/0x9b0 fs/namei.c:4477
do_unlinkat+0x53e/0x730 fs/namei.c:4541
__x64_sys_unlink+0xc6/0x110 fs/namei.c:4587
do_syscall_64+0xf5/0x220 arch/x86/entry/common.c:78
entry_SYSCALL_64_after_hwframe+0x77/0x7f
WARNING: CPU: 0 PID: 646 at fs/inode.c:336 drop_nlink+0xad/0xd0 fs/inode.c:336
CPU: 0 UID: 0 PID: 646 Comm: syz.0.17 Not tainted 6.12.77+ #1
Call Trace:
inode_dec_link_count include/linux/fs.h:2518 [inline]
ext2_rename+0x35e/0x850 fs/ext2/namei.c:374
vfs_rename+0xf2f/0x2060 fs/namei.c:5021
do_renameat2+0xbe2/0xd50 fs/namei.c:5178
__x64_sys_rename+0x7e/0xa0 fs/namei.c:5223
do_syscall_64+0xf5/0x220 arch/x86/entry/common.c:78
entry_SYSCALL_64_after_hwframe+0x77/0x7f
WARNING: CPU: 0 PID: 634 at fs/inode.c:336 drop_nlink+0xad/0xd0 fs/inode.c:336
CPU: 0 UID: 0 PID: 634 Comm: syz-executor Not tainted 6.12.77+ #1
Call Trace:
inode_dec_link_count include/linux/fs.h:2518 [inline]
ext2_rmdir+0xca/0x110 fs/ext2/namei.c:311
vfs_rmdir+0x204/0x690 fs/namei.c:4348
do_rmdir+0x372/0x3e0 fs/namei.c:4407
__x64_sys_unlinkat+0xf0/0x130 fs/namei.c:4577
do_syscall_64+0xf5/0x220 arch/x86/entry/common.c:78
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Extend the existing i_nlink == 0 check to also catch this case,
reporting the corruption via ext2_error() and returning -EFSCORRUPTED.
This rejects the inode at load time and prevents it from reaching any
of the namei.c paths.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
A flaw was found in the Linux kernel's ext2 filesystem. A local attacker could create a specially crafted filesystem image with malformed inodes (index nodes) that, when mounted, would not be properly rejected by the ext2_iget() function. This could lead to a kernel warning and potentially a system crash, resulting in a Denial of Service (DoS).
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Not affected | ||
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected |
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Дополнительная информация
Статус:
EPSS
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: ext2: reject inodes with zero i_nlink and valid mode in ext2_iget() ext2_iget() already rejects inodes with i_nlink == 0 when i_mode is zero or i_dtime is set, treating them as deleted. However, the case of i_nlink == 0 with a non-zero mode and zero dtime slips through. Since ext2 has no orphan list, such a combination can only result from filesystem corruption - a legitimate inode deletion always sets either i_dtime or clears i_mode before freeing the inode. A crafted image can exploit this gap to present such an inode to the VFS, which then triggers WARN_ON inside drop_nlink() (fs/inode.c) via ext2_unlink(), ext2_rename() and ext2_rmdir(): WARNING: CPU: 3 PID: 609 at fs/inode.c:336 drop_nlink+0xad/0xd0 fs/inode.c:336 CPU: 3 UID: 0 PID: 609 Comm: syz-executor Not tainted 6.12.77+ #1 Call Trace: <TASK> inode_dec_link_count include/linux/fs.h:2518 [inline] ext2_unlink+0x26c/0x300 fs/ext2/namei.c:295 vfs_unlink+0x2fc/...
In the Linux kernel, the following vulnerability has been resolved: ext2: reject inodes with zero i_nlink and valid mode in ext2_iget() ext2_iget() already rejects inodes with i_nlink == 0 when i_mode is zero or i_dtime is set, treating them as deleted. However, the case of i_nlink == 0 with a non-zero mode and zero dtime slips through. Since ext2 has no orphan list, such a combination can only result from filesystem corruption - a legitimate inode deletion always sets either i_dtime or clears i_mode before freeing the inode. A crafted image can exploit this gap to present such an inode to the VFS, which then triggers WARN_ON inside drop_nlink() (fs/inode.c) via ext2_unlink(), ext2_rename() and ext2_rmdir(): WARNING: CPU: 3 PID: 609 at fs/inode.c:336 drop_nlink+0xad/0xd0 fs/inode.c:336 CPU: 3 UID: 0 PID: 609 Comm: syz-executor Not tainted 6.12.77+ #1 Call Trace: <TASK> inode_dec_link_count include/linux/fs.h:2518 [inline] ext2_unlink+0x26c/0x300 fs/ext2/namei.c:295 vfs_unlink+0
ext2: reject inodes with zero i_nlink and valid mode in ext2_iget()
In the Linux kernel, the following vulnerability has been resolved: e ...
In the Linux kernel, the following vulnerability has been resolved: ext2: reject inodes with zero i_nlink and valid mode in ext2_iget() ext2_iget() already rejects inodes with i_nlink == 0 when i_mode is zero or i_dtime is set, treating them as deleted. However, the case of i_nlink == 0 with a non-zero mode and zero dtime slips through. Since ext2 has no orphan list, such a combination can only result from filesystem corruption - a legitimate inode deletion always sets either i_dtime or clears i_mode before freeing the inode. A crafted image can exploit this gap to present such an inode to the VFS, which then triggers WARN_ON inside drop_nlink() (fs/inode.c) via ext2_unlink(), ext2_rename() and ext2_rmdir(): WARNING: CPU: 3 PID: 609 at fs/inode.c:336 drop_nlink+0xad/0xd0 fs/inode.c:336 CPU: 3 UID: 0 PID: 609 Comm: syz-executor Not tainted 6.12.77+ #1 Call Trace: <TASK> inode_dec_link_count include/linux/fs.h:2518 [inline] ext2_unlink+0x26c/0x300 fs/ext2/namei.c:295 vfs_unlin...
EPSS
5.5 Medium
CVSS3