CVE-2022-50478 nilfs2: fix shift-out-of-bounds/overflow in nilfs_sb2_bad_offset()
A corrupted superblock in the nilfs2 filesystem can cause a shift-out-of-bounds error and kernel panic, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-50478?
CVE-2022-50478 is a high-severity vulnerability in Linux kernel, published on 4 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
nilfs2: fix shift-out-of-bounds/overflow in nilfs_sb2_bad_offset()
Patch series "nilfs2: fix UBSAN shift-out-of-bounds warnings on mount time".
The first patch fixes a bug reported by syzbot, and the second one fixes the remaining bug of the same kind. Although they are triggered by the same super block data anomaly, I divided it into the above two because the details of the issues and how to fix it are different.
Both are required to eliminate the shift-out-of-bounds issues at mount time.
This patch (of 2):
If the block size exponent information written in an on-disk superblock is corrupted, nilfs_sb2_bad_offset helper function can trigger shift-out-of-bounds warning followed by a kernel panic (if panic_on_warn is set):
shift exponent 38983 is too large for 64-bit type 'unsigned long long' Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106 ubsan_epilogue lib/ubsan.c:151 [inline] __ubsan_handle_shift_out_of_bounds+0x33d/0x3b0 lib/ubsan.c:322 nilfs_sb2_bad_offset fs/nilfs2/the_nilfs.c:449 [inline] nilfs_load_super_block+0xdf5/0xe00 fs/nilfs2/the_nilfs.c:523 init_nilfs+0xb7/0x7d0 fs/nilfs2/the_nilfs.c:577 nilfs_fill_super+0xb1/0x5d0 fs/nilfs2/super.c:1047 nilfs_mount+0x613/0x9b0 fs/nilfs2/super.c:1317 ...
In addition, since nilfs_sb2_bad_offset() performs multiplication without considering the upper bound, the computation may overflow if the disk layout parameters are not normal.
This fixes these issues by inserting preliminary sanity checks for those parameters and by converting the comparison from one involving multiplication and left bit-shifting to one using division and right bit-shifting.
Weakness: CWE-125
Which versions are affected by CVE-2022-50478?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-50478?
Apply the vendor's patch.
Is CVE-2022-50478 being exploited?
There is no known exploitation of CVE-2022-50478 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-50478, GHSA-2gq6-55f4-4v54, UBUNTU-CVE-2022-50478.