CVE-2026-80536

Summary

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

xfs: bounds-check buffer log item's dirty bitmap

xlog_recover_do_reg_buffer() replays each dirty region described by a buffer log item's bitmap into the buffer read for that item:

memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT),
	item->ri_buf[i].iov_base,
	nbits << XFS_BLF_SHIFT);

The destination offset (bit/nbits, from the logged dirty bitmap) and the buffer size (from the logged blf_len) are both attacker-controlled and otherwise unrelated, yet the only thing bounding the copy is an ASSERT(), which compiles away on production kernels. A crafted image logging a small blf_len together with a bitmap bit past the end of that buffer drives the memcpy() past the buffer's allocation, corrupting adjacent kernel heap during mount-time log recovery. This is reachable by anyone who can get a crafted image mounted – the malicious-filesystem threat model XFS already guards against elsewhere.

Turn the ASSERT() into a real XFS_IS_CORRUPT() check that aborts recovery of the buffer with -EFSCORRUPTED, consistent with the validate-and-fail idiom already used in xlog_recover_do_inode_buffer() and xfs_dquot_item_recover.c. xlog_recover_do_reg_buffer() therefore becomes STATIC int and its three callers propagate the error.

Found and confirmed with KASAN on a CONFIG_XFS_DEBUG=n build: the crafted image trips a slab-out-of-bounds write before this change and fails recovery cleanly with -EFSCORRUPTED after it.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/f8288214459ead7e87d26e5822f62c14a4f2ed6b
• https://git.kernel.org/stable/c/edaf5b6bd625356893da20d69a259b34a9de2694
• https://git.kernel.org/stable/c/813f8136a2ce1fee266d02a7df73db6e8a541604

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