cxl/features: bound fwctl command payload to the input buffer

Overview

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

cxl/features: bound fwctl command payload to the input buffer

fwctl_cmd_rpc() copies cmd->in_len bytes into inbuf = kvzalloc(cmd->in_len) and passes inbuf and in_len to ->fw_rpc(). The CXL callback cxlctl_fw_rpc() ignores in_len and never checks the user-controlled op_size against it.

cxlctl_set_feature() bounds op_size only from below (op_size <= sizeof(feat_in->hdr)) and then reads op_size - sizeof(hdr) bytes from feat_in->feat_data via cxl_set_feature(). With a small in_len and a large op_size the first memcpy() already reads past the kvzalloc(in_len) buffer; the out-of-bounds bytes are placed in the mailbox payload and sent to the device, and a large enough op_size can walk into unmapped memory and oops the kernel. The Get paths pin op_size to a fixed size but likewise read the input struct without checking in_len.

Reject, at the single dispatch point, any request whose fixed header plus op_size does not fit in the copied-in buffer. The lower-bound test guards the subtraction and ensures op_size was copied in before it is read.

Affected

• Linux >= eb5dfcb9e36d0e46089fec777d911313c1876fa3 < 14d52c15d5d99477b20a2d61fe36f347080da6cd
• Linux >= eb5dfcb9e36d0e46089fec777d911313c1876fa3 < d8957545fe96f7905791c937758ebfc1ae1e5b17
• Linux >= eb5dfcb9e36d0e46089fec777d911313c1876fa3 < f687394af983df5660b6afae7e0d06969f3af206
• Linux 6.15

Remediation

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

Vendor advisories

• Red Hat VEX · Moderate · updated 2026-09-18 · vex