CVE-2026-64187: xfs: fail recovery on a committed log item with no regions

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

xfs: fail recovery on a committed log item with no regions

If the first op of a transaction is a bare transaction header (len == sizeof(struct xfstransheader)), xlogrecoveraddtotrans() adds an item but no region, leaving it on ritemq with ricnt == 0 and ribuf == NULL.

The header can be split across op records, so later ops may still add regions; the item is only invalid if the transaction commits with none. The runtime commit path never emits such a transaction, so this only happens on a crafted log. It came from an AI-assisted code audit of the recovery parser.

xlogrecoverreordertrans() calls ITEMTYPE() on the item, which reads (unsigned short )item->ribuf[0].iovbase and faults on the NULL ribuf. Reject it there, before the commit handlers that also read ribuf[0].

KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:xlogrecoverreordertrans (fs/xfs/xfslogrecover.c:1836) xlogrecovercommittrans (fs/xfs/xfslogrecover.c:2043) xlogrecoverprocessdata (fs/xfs/xfslogrecover.c:2501) xlogdorecoverypass (fs/xfs/xfslogrecover.c:3244) xlogrecover (fs/xfs/xfslogrecover.c:3493) xfslogmount (fs/xfs/xfslog.c:618) xfsmountfs (fs/xfs/xfsmount.c:1034) xfsfsfillsuper (fs/xfs/xfssuper.c:1938) vfsgettree (fs/super.c:1695) pathmount (fs/namespace.c:4161) x64sysmount (fs/namespace.c:4367)