CVE-2026-53130

Summary

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

fs/omfs: reject s_sys_blocksize smaller than OMFS_DIR_START

omfs_fill_super() rejects oversized s_sys_blocksize values (> PAGE_SIZE), but it does not reject values smaller than OMFS_DIR_START (0x1b8 = 440).

Later, omfs_make_empty() uses

sbi->s_sys_blocksize - OMFS_DIR_START

as the length argument to memset(). Since s_sys_blocksize is u32, a crafted filesystem image with s_sys_blocksize < OMFS_DIR_START causes an unsigned underflow there, wrapping to a value near 2^32. That drives a ~4 GiB memset() from bh->b_data + OMFS_DIR_START and overwrites kernel memory far beyond the backing block buffer.

Add the corresponding lower-bound check alongside the existing upper-bound check in omfs_fill_super(), so that malformed images are rejected during superblock validation before any filesystem data is processed.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/fbc72f5c645155dc2ed3573243ed20f9913e3a54
• https://git.kernel.org/stable/c/5822a05a841a10794ad818620dd2af490b0705d3
• https://git.kernel.org/stable/c/754ff1bea3819a90c6f33cccfc1a299ef7609f07
• https://git.kernel.org/stable/c/131ea3e57fc22936ed0e2c8330f2e36106172f51
• https://git.kernel.org/stable/c/79f84af38c9fef9deb0e02c79eb969b5541c2644
• https://git.kernel.org/stable/c/6561afc38398e3518a29c5eebb975c30468f98a6
• https://git.kernel.org/stable/c/817f16ed62bc58a168417bfb5e859c2a370bab03
• https://git.kernel.org/stable/c/0621c385fda1376e967f37ccd534c26c3e511d14

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