Linux EUVD-2026-81811

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

RDMA/cma: Fix WARNING in res_to_rt

syzbot reported a WARN_ON(!res->dev) in res_to_rt() triggered via addr_handler() during asynchronous address resolution:

" WARNING: drivers/infiniband/core/restrack.c:138 at res_to_rt+0x1c4/0x230 CPU#1: kworker/u8:4/59 Modules linked in: CPU: 1 UID: 0 PID: 59 Comm: kworker/u8:4 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Compute Engine, BIOS Google 07/24/2026 Workqueue: ib_addr process_one_req RIP: 0010:res_to_rt+0x1c4/0x230 drivers/infiniband/core/restrack.c:138 RSP: 0018:ffffc9000201f850 EFLAGS: 00010293 RAX: ffffffff88d00ce5 RBX: ffff88807f0fd4f8 RCX: ffff88801e6e0000 RDX: 0000000000000000 RSI: ffffffff8fd996f0 RDI: 0000000000000003 RBP: 0000000000000000 R08: ffff88801e6e0000 R09: 000000000000000a R10: 0000000000000009 R11: 0000000000000000 R12: dffffc0000000000 R13: 1ffff1100fe1fa9f R14: 0000000000000000 R15: 0000000000000003 FS: 0000000000000000(0000) GS:ffff888125012000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00001d559c3d2000 CR3: 0000000077c4c000 CR4: 00000000003526f0 Call Trace: <TASK> rdma_restrack_add+0x5a/0x8a0 drivers/infiniband/core/restrack.c:236 addr_handler+0x41a/0x5a0 drivers/infiniband/core/cma.c:3534 process_one_req+0x2eb/0x540 drivers/infiniband/core/addr.c:624 process_one_work kernel/workqueue.c:3375 [inline] process_scheduled_works+0xc4e/0x1630 kernel/workqueue.c:3458 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3539 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> "

In addr_handler(), cma_acquire_dev_by_src_ip() is called to populate id_priv->cma_dev and bind the associated ib_device to id_priv->id.device. If cma_acquire_dev_by_src_ip() returns an error (non-zero status), the ID remains unassociated with any RDMA device.

Previously, rdma_restrack_add(&id_priv->res) was invoked unconditionally even when cma_acquire_dev_by_src_ip() failed, passing a resource with a NULL dev pointer and triggering the WARN_ON assertion in res_to_rt().

Fix this by only adding the resource to restrack when acquiring the device succeeds.