CVE-2026-46114

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

RDMA/rxe: Reject non-8-byte ATOMIC_WRITE payloads

atomic_write_reply() at drivers/infiniband/sw/rxe/rxe_resp.c

unconditionally dereferences 8 bytes at payload_addr(pkt):

value = *(u64 *)payload_addr(pkt);

check_rkey() previously accepted an ATOMIC_WRITE request with pktlen ==

resid == 0 because the length validation only compared pktlen against

resid. A remote initiator that sets the RETH length to 0 therefore reaches

atomic_write_reply() with a zero-byte logical payload, and the responder

reads sizeof(u64) bytes from past the logical end of the packet into

skb->head tailroom, then writes those 8 bytes into the attacker's MR via

rxe_mr_do_atomic_write(). That is a remote disclosure of 4 bytes of kernel

tailroom per probe (the other 4 bytes are the packet's own trailing ICRC).

IBA oA19-28 defines ATOMIC_WRITE as exactly 8 bytes. Anything else is

protocol-invalid. Hoist a strict length check into check_rkey() so the

responder never reaches the unchecked dereference, and keep the existing

WRITE-family length logic for the normal RDMA WRITE path.

Reproduced on mainline with an unmodified rxe driver: a sustained

zero-length ATOMIC_WRITE probe repeatedly leaks adjacent skb head-buffer

bytes into the attacker's MR, including recognisable kernel strings and

partial kernel-direct-map pointer words. With this patch applied the

responder rejects the PDU and the MR stays all-zero.