CVE-2023-53763
Description
In the Linux kernel, the following vulnerability has been resolved:
Revert "f2fs: fix to do sanity check on extent cache correctly"
syzbot reports a f2fs bug as below:
UBSAN: array-index-out-of-bounds in fs/f2fs/f2fs.h:3275:19 index 1409 is out of range for type '__le32[923]' (aka 'unsigned int[923]') Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106 ubsan_epilogue lib/ubsan.c:217 [inline] __ubsan_handle_out_of_bounds+0x11c/0x150 lib/ubsan.c:348 inline_data_addr fs/f2fs/f2fs.h:3275 [inline] __recover_inline_status fs/f2fs/inode.c:113 [inline] do_read_inode fs/f2fs/inode.c:480 [inline] f2fs_iget+0x4730/0x48b0 fs/f2fs/inode.c:604 f2fs_fill_super+0x640e/0x80c0 fs/f2fs/super.c:4601 mount_bdev+0x276/0x3b0 fs/super.c:1391 legacy_get_tree+0xef/0x190 fs/fs_context.c:611 vfs_get_tree+0x8c/0x270 fs/super.c:1519 do_new_mount+0x28f/0xae0 fs/namespace.c:3335 do_mount fs/namespace.c:3675 [inline] __do_sys_mount fs/namespace.c:3884 [inline] __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3861 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
The issue was bisected to:
commit d48a7b3a72f121655d95b5157c32c7d555e44c05 Author: Chao Yu <chao@kernel.org> Date: Mon Jan 9 03:49:20 2023 +0000
f2fs: fix to do sanity check on extent cache correctly
The root cause is we applied both v1 and v2 of the patch, v2 is the right fix, so it needs to revert v1 in order to fix reported issue.
v1: commit d48a7b3a72f1 ("f2fs: fix to do sanity check on extent cache correctly") https://lore.kernel.org/lkml/20230109034920.492914-1-chao@kernel.org/
v2: commit 269d11948100 ("f2fs: fix to do sanity check on extent cache correctly") https://lore.kernel.org/lkml/20230207134808.1827869-1-chao@kernel.org/
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A reverted f2fs sanity check patch in the Linux kernel caused an out-of-bounds array access via UBSAN, exploitable by mounting a crafted f2fs image.
CVE-2023-53763 is a vulnerability in the Linux kernel's f2fs (Flash-Friendly File System) filesystem. The root cause is a buggy commit (d48a7b3a72f1) that attempted to add a sanity check on the extent cache but introduced an out-of-bounds array access. The check was incorrectly implemented, and a later correct version (269d11948100) was applied without removing the first, leading to a double-fix scenario that triggered a UBSAN warning.
Exploitation
An attacker can trigger the vulnerability by mounting a specially crafted f2fs filesystem image. The out-of-bounds read occurs in the inline_data_addr() function when the kernel is recovering inline status during inode loading (do_read_inode). The issue manifests as an array-index-out-of-bounds error, as reported by syzbot [1]. No authentication or local access beyond mounting a filesystem is required; the attack surface is a malicious storage device or image.
Impact
Successful exploitation could lead to a system crash (denial of service) due to the UBSAN-detected out-of-bounds access. In older kernels without UBSAN or with below-minimum image size, the behavior might be undefined, potentially facilitating information disclosure or privilege escalation, though the advisory focuses on the crash [1][2]. The fix is to revert the problematic commit, ensuring only the correct version of the sanity check is applied.
Mitigation
The Linux kernel upstream has resolved this by reverting commit d48a7b3a72f1 [1]. The fix was applied to the stable kernel tree, as seen in the referenced stable commit [2]. Users should update to a kernel version including this revert. No workaround is available; the vulnerability is only triggered during filesystem mount with a malicious image.
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
2Patches
40d545a8e77cbea35767edc78bbb3cd66301e958ccbbf1ce7Vulnerability mechanics
Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
4News mentions
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