CVE-2022-49763 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
ntfs: fix use-after-free in ntfs_attr_find()
Patch series "ntfs: fix bugs about Attribute", v2.
This patchset fixes three bugs relative to Attribute in record:
Patch 1 adds a sanity check to ensure that, attrs_offset field in first mft record loading from disk is within bounds.
Patch 2 moves the ATTR_RECORD's bounds checking earlier, to avoid dereferencing ATTR_RECORD before checking this ATTR_RECORD is within bounds.
Patch 3 adds an overflow checking to avoid possible forever loop in ntfs_attr_find().
Without patch 1 and patch 2, the kernel triggersa KASAN use-after-free detection as reported by Syzkaller.
Although one of patch 1 or patch 2 can fix this, we still need both of them. Because patch 1 fixes the root cause, and patch 2 not only fixes the direct cause, but also fixes the potential out-of-bounds bug.
This patch (of 3):
Syzkaller reported use-after-free read as follows: ================================================================== BUG: KASAN: use-after-free in ntfs_attr_find+0xc02/0xce0 fs/ntfs/attrib.c:597 Read of size 2 at addr ffff88807e352009 by task syz-executor153/3607
[...]
Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:317 [inline]
print_report.cold+0x2ba/0x719 mm/kasan/report.c:433 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495 ntfs_attr_find+0xc02/0xce0 fs/ntfs/attrib.c:597 ntfs_attr_lookup+0x1056/0x2070 fs/ntfs/attrib.c:1193 ntfs_read_inode_mount+0x89a/0x2580 fs/ntfs/inode.c:1845 ntfs_fill_super+0x1799/0x9320 fs/ntfs/super.c:2854 mount_bdev+0x34d/0x410 fs/super.c:1400 legacy_get_tree+0x105/0x220 fs/fs_context.c:610 vfs_get_tree+0x89/0x2f0 fs/super.c:1530 do_new_mount fs/namespace.c:3040 [inline]
path_mount+0x1326/0x1e20 fs/namespace.c:3370 do_mount fs/namespace.c:3383 [inline]
__do_sys_mount fs/namespace.c:3591 [inline]
__se_sys_mount fs/namespace.c:3568 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3568 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...]
</TASK>
The buggy address belongs to the physical page: page:ffffea0001f8d400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7e350 head:ffffea0001f8d400 order:3 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888011842140 raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88807e351f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88807e351f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88807e352000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88807e352080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88807e352100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
Kernel will loads $MFT/$DATA's first mft record in ntfs_read_inode_mount().
Yet the problem is that after loading, kernel doesn't check whether attrs_offset field is a valid value.
To be more specific, if attrs_offset field is larger than bytes_allocated field, then it may trigger the out-of-bounds read bug(reported as use-after-free bug) in ntfs_attr_find(), when kernel tries to access the corresponding mft record's attribute.
This patch solves it by adding the sanity check between attrs_offset field and bytes_allocated field, after loading the first mft record.
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Analysis
by VulDB Data Team • 11/07/2025
The vulnerability CVE-2022-49763 represents a critical use-after-free condition in the Linux kernel's NTFS filesystem driver, specifically within the ntfs_attr_find() function. This flaw arises from inadequate bounds checking during the processing of Master File Table (MFT) records, creating a path for memory corruption that can be exploited by malicious actors. The issue stems from the ntfs filesystem implementation's failure to validate the attrs_offset field against the bytes_allocated field when loading the first MFT record from disk, leading to out-of-bounds memory access patterns that trigger kernel memory safety mechanisms.
The technical root cause manifests when the kernel loads the initial MFT record without validating that the attrs_offset field falls within acceptable bounds defined by bytes_allocated. This validation gap allows for scenarios where attrs_offset exceeds bytes_allocated, creating a condition where subsequent calls to ntfs_attr_find() attempt to access memory beyond the allocated buffer boundaries. The KASAN (Kernel Address Sanitizer) detection confirms this behavior with a use-after-free read error at address 0xffff88807e352009, where the kernel attempts to read 2 bytes from memory that has already been freed or is otherwise inaccessible. This particular memory access pattern follows a call chain that begins with ntfs_read_inode_mount() and progresses through ntfs_attr_lookup() before reaching the vulnerable ntfs_attr_find() function.
The patch series addressing this vulnerability implements three distinct fixes to prevent the memory safety violations. Patch 1 introduces a sanity check to ensure the attrs_offset field remains within valid bounds after loading the first MFT record, directly addressing the root cause of the issue. Patch 2 relocates ATTR_RECORD bounds checking to an earlier execution point to prevent dereferencing invalid memory locations before validation occurs. Patch 3 adds overflow checking to prevent potential infinite loops in ntfs_attr_find() that could occur under malformed input conditions. These patches work together to provide comprehensive protection, with the first two patches being essential for preventing the specific use-after-free condition while the third provides additional robustness against other potential edge cases.
From an operational security perspective, this vulnerability presents a significant risk to Linux systems that mount NTFS filesystems, particularly those running kernel versions affected by this issue. The vulnerability could be exploited to cause system crashes or potentially enable privilege escalation attacks, though the exact attack vectors depend on the specific system configuration and available attack surface. The use of Syzkaller for detection indicates this is a sophisticated issue that requires careful memory management validation. The vulnerability aligns with CWE-416 (Use After Free) and CWE-129 (Improper Validation of Array Index) classifications, and could potentially map to ATT&CK techniques involving privilege escalation or system instability through kernel memory corruption. Organizations should prioritize patching affected systems and monitoring for potential exploitation attempts, particularly in environments where NTFS filesystems are mounted or where kernel memory safety violations are detected.