CVE-2026-52939net/rds: fix NULL deref in rds_ib_send_cqe_handler() on masked atomic completion

Official description

In the Linux kernel, the following vulnerability has been resolved: net/rds: fix NULL deref in rds_ib_send_cqe_handler() on masked atomic completion rds_ib_xmit_atomic() always programs a masked atomic opcode (IB_WR_MASKED_ATOMIC_CMP_AND_SWP or IB_WR_MASKED_ATOMIC_FETCH_AND_ADD) for every RDS atomic cmsg. But the completion-side switch in rds_ib_send_unmap_op() only handles the non-masked opcodes, so a masked atomic completion falls through to default and returns rm == NULL while send->s_op is left set. rds_ib_send_cqe_handler() then dereferences the NULL rm via rm->m_final_op, oopsing in softirq context. An unprivileged AF_RDS sendmsg() of an atomic cmsg over an active RDS/IB connection triggers it; on hardware that natively accepts masked atomics (mlx4, mlx5) no extra setup is needed. RDS/IB: rds_ib_send_unmap_op: unexpected opcode 0xd in WR! Oops: general protection fault [#1] SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000190-0x0000000000000197] RIP: rds_ib_send_cqe_handler+0x25c/0xb10 (net/rds/ib_send.c:282) Call Trace: <IRQ> rds_ib_send_cqe_handler (net/rds/ib_send.c:282) poll_scq (net/rds/ib_cm.c:274) rds_ib_tasklet_fn_send (net/rds/ib_cm.c:294) tasklet_action_common (kernel/softirq.c:943) handle_softirqs (kernel/softirq.c:573) run_ksoftirqd (kernel/softirq.c:479) </IRQ> Kernel panic - not syncing: Fatal exception in interrupt Handle the masked atomic opcodes in the same case as the non-masked ones: they map to the same struct rds_message.atomic union member, so the existing container_of()/rds_ib_send_unmap_atomic() body is correct for them.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/a0148342badd8c9b2e46551766a27cb76c82e715
• https://git.kernel.org/stable/c/4dd262f875e87653df50b138de1390ab0628e6b7
• https://git.kernel.org/stable/c/6e4615164d185a26badb2f376a2449f4d174a5f0
• https://git.kernel.org/stable/c/0f22412a2f4fbbe0251c132abee045d15a90e5b6
• https://git.kernel.org/stable/c/0f7baa82a24813cdad0b06a6f8f07e4824af5ed5
• https://git.kernel.org/stable/c/dcf458120add64c96a6ef5cf719340453f6e6abf
• https://git.kernel.org/stable/c/4fd34669558085bcb589aa2078a13b0ca79e360d
• https://git.kernel.org/stable/c/34080db3e70ddf94c38512ad2331e3c3afca6cc1