CVE-2026-72217

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

SUNRPC: Bound-check xdrbufto_bvec() stores before writing

xdrbuftobvec() writes a biovec into the caller's array before

testing whether that slot is in range, and the head branch performs

the store with no check at all. When the caller's budget is exactly

used up, the next store lands one element past the end of the array.

The overflow label returns count - 1, which masks the surplus store

but cannot undo it.

rqbvec, the array passed by nfsdvfs_write(), is allocated to

exactly rq_maxpages entries with no slack. The OOB store can land in

adjacent slab memory; the bvlen and bvoffset fields written there

are derived from client-supplied RPC payload sizes.

Move the in-range check ahead of the store in the head, page-loop,

and tail branches. With the check at the top of each sequence, count

is incremented only after a successful store, so the overflow label

can return count directly.