RDMA/uverbs: Validate wqe_size before using it in ib_uverbs_post_send

Overview

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).

Affected

• Linux >= c3bea3d2dc5358e05541527283279102383b0231 < 9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7
• Linux >= c3bea3d2dc5358e05541527283279102383b0231 < 9b5ac1c15334d46c0dbd49d64a2257b929500163
• Linux >= c3bea3d2dc5358e05541527283279102383b0231 < 01c9b152647dc70dc06a4a2eff86ebb3b3c76075
• Linux >= c3bea3d2dc5358e05541527283279102383b0231 < bf1feed1a7886af945f92890493aefd2b5c9928a
• Linux >= c3bea3d2dc5358e05541527283279102383b0231 < d533425ac1f2925b4fc3e4ed9b9d72362cb23475
• Linux >= c3bea3d2dc5358e05541527283279102383b0231 < bf4454da8b1e712714628c0a0d6e7845bb40790a
• Linux >= c3bea3d2dc5358e05541527283279102383b0231 < bef70ff9841990658610512b4a18e4a88c9b4df6
• Linux >= c3bea3d2dc5358e05541527283279102383b0231 < 1956f0a74ccf5dc9c3ef717f2985c3ed3400aab0
• Linux 5.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.