CVE-2026-72464

Status: UPDATED  |  Advisory ID: CVE-2026-72464

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

xprtrdma: Repost Receive buffers for malformed replies

rpcrdma_wc_receive() decrements the transport's Receive count for

every completion before it dispatches a successful Receive to

rpcrdma_reply_handler(). The handler must post a replacement

Receive WR before returning unless ownership of the rep has moved

elsewhere, as on the backchannel path.

Commit 2ae50ad68cd7 ("xprtrdma: Close window between waking RPC

senders and posting Receives") moved the Receive refill out of

rpcrdma_wc_receive(), where it had run ahead of every reply, into

rpcrdma_reply_handler() so that the responder's credit grant could

be parsed before reposting. The bad-version and short-reply exits

never reach that refill: they recycle the rep and return without

calling rpcrdma_post_recvs().

A remote peer can therefore drain the client's posted Receive

queue by sending a sustained stream of replies that are shorter

than the fixed transport header or that carry an unrecognized

RPC/RDMA version. Each such reply consumes one posted Receive

without replacing it. Once the queue empties, the peer's next

Send finds no posted Receive and the transport stalls until

reconnect.

Route both malformed-reply exits through the shared repost tail

after recycling the rep, refilling against buf->rb_credits, the

most recent accepted credit grant. Neither exit updates the

congestion window, so RPCs admitted under the previous grant

remain in flight awaiting replies. A smaller refill target would

let a stream of malformed replies ratchet the posted Receive count

down to the batch floor while the congestion window still admits

rb_credits RPCs; a burst of valid replies to those RPCs could then

overrun the posted Receives, and because the client connects with

rnr_retry_count of zero, a single RNR NAK terminates the

connection. Refilling against rb_credits also restores the target

that applied to malformed replies before commit 2ae50ad68cd7

("xprtrdma: Close window between waking RPC senders and posting

Receives") when rpcrdma_post_recvs() computed it from rb_credits

internally. rb_credits is at least one from connection

establishment onward, so the repost path always keeps Receives

posted. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References