CVE-2025-22121

In the Linux kernel, the following vulnerability has been resolved:

ext4: fix out-of-bound read in ext4_xattr_inode_dec_ref_all()

There's issue as follows: BUG: KASAN: use-after-free in ext4_xattr_inode_dec_ref_all+0x6ff/0x790 Read of size 4 at addr ffff88807b003000 by task syz-executor.0/15172

CPU: 3 PID: 15172 Comm: syz-executor.0 Call Trace: __dump_stack lib/dump_stack.c:82 [inline] dump_stack+0xbe/0xfd lib/dump_stack.c:123 print_address_description.constprop.0+0x1e/0x280 mm/kasan/report.c:400 __kasan_report.cold+0x6c/0x84 mm/kasan/report.c:560 kasan_report+0x3a/0x50 mm/kasan/report.c:585 ext4_xattr_inode_dec_ref_all+0x6ff/0x790 fs/ext4/xattr.c:1137 ext4_xattr_delete_inode+0x4c7/0xda0 fs/ext4/xattr.c:2896 ext4_evict_inode+0xb3b/0x1670 fs/ext4/inode.c:323 evict+0x39f/0x880 fs/inode.c:622 iput_final fs/inode.c:1746 [inline] iput fs/inode.c:1772 [inline] iput+0x525/0x6c0 fs/inode.c:1758 ext4_orphan_cleanup fs/ext4/super.c:3298 [inline] ext4_fill_super+0x8c57/0xba40 fs/ext4/super.c:5300 mount_bdev+0x355/0x410 fs/super.c:1446 legacy_get_tree+0xfe/0x220 fs/fs_context.c:611 vfs_get_tree+0x8d/0x2f0 fs/super.c:1576 do_new_mount fs/namespace.c:2983 [inline] path_mount+0x119a/0x1ad0 fs/namespace.c:3316 do_mount+0xfc/0x110 fs/namespace.c:3329 __do_sys_mount fs/namespace.c:3540 [inline] __se_sys_mount+0x219/0x2e0 fs/namespace.c:3514 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x67/0xd1

Memory state around the buggy address: ffff88807b002f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88807b002f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

ffff88807b003000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff88807b003080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88807b003100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

Above issue happens as ext4_xattr_delete_inode() isn't check xattr is valid if xattr is in inode. To solve above issue call xattr_check_inode() check if xattr if valid in inode. In fact, we can directly verify in ext4_iget_extra_inode(), so that there is no divergent verification.

This vulnerability is rated as having Moderate impact because exploitation requires mounting a maliciously crafted ext4 filesystem, which is a privileged administrative operation by default on Red Hat Enterprise Linux. An unprivileged local user cannot trigger this flaw unless granted explicit mounting capabilities or delegated privileges. Although a successful exploit could trigger a kernel crash or disclose kernel memory, the high privileges required to mount custom block devices substantially limit the exposure on standard deployments.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.