CVE-2026-45856

Description

In the Linux kernel, the following vulnerability has been resolved: RDMA/uverbs: Validate wqe_size before using it in ib_uverbs_post_send ib_uverbs_post_send() uses cmd.wqe_size from userspace without any validation before passing it to kmalloc() and using the allocated buffer as struct ib_uverbs_send_wr. If a user provides a small wqe_size value (e.g., 1), kmalloc() will succeed, but subsequent accesses to user_wr->opcode, user_wr->num_sge, and other fields will read beyond the allocated buffer, resulting in an out-of-bounds read from kernel heap memory. This could potentially leak sensitive kernel information to userspace. Additionally, providing an excessively large wqe_size can trigger a WARNING in the memory allocation path, as reported by syzkaller. This is inconsistent with ib_uverbs_unmarshall_recv() which properly validates that wqe_size >= sizeof(struct ib_uverbs_recv_wr) before proceeding. Add the same validation for ib_uverbs_post_send() to ensure wqe_size is at least sizeof(struct ib_uverbs_send_wr).

Predictions

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

References

• https://git.kernel.org/stable/c/9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7
• https://git.kernel.org/stable/c/9b5ac1c15334d46c0dbd49d64a2257b929500163
• https://git.kernel.org/stable/c/01c9b152647dc70dc06a4a2eff86ebb3b3c76075
• https://git.kernel.org/stable/c/bf1feed1a7886af945f92890493aefd2b5c9928a
• https://git.kernel.org/stable/c/d533425ac1f2925b4fc3e4ed9b9d72362cb23475
• https://git.kernel.org/stable/c/bf4454da8b1e712714628c0a0d6e7845bb40790a
• https://git.kernel.org/stable/c/bef70ff9841990658610512b4a18e4a88c9b4df6
• https://git.kernel.org/stable/c/1956f0a74ccf5dc9c3ef717f2985c3ed3400aab0
• https://security-tracker.debian.org/tracker/CVE-2026-45856
• https://www.suse.com/security/cve/CVE-2026-45856.html