CVE-2026-80536xfs: bounds-check buffer log item's dirty bitmap

Official description

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 packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/acb4e26295e7f0e685815a3fd3d70bd8329cefa1
• https://git.kernel.org/stable/c/f3859c35a4fbc1c1c58431f684f808e43696891d
• https://git.kernel.org/stable/c/f7b5fa83e2c192be922121b764415fa8c7549ea1
• https://git.kernel.org/stable/c/b7528b42813f02724a78fce1da24d69d1bfc4d38
• https://git.kernel.org/stable/c/7e32d4eebae6ca24f8a673c107fd7eca1f47afc2
• https://git.kernel.org/stable/c/f8288214459ead7e87d26e5822f62c14a4f2ed6b
• https://git.kernel.org/stable/c/edaf5b6bd625356893da20d69a259b34a9de2694
• https://git.kernel.org/stable/c/813f8136a2ce1fee266d02a7df73db6e8a541604