From 8a13db9f899d149c3aab24abcb668121cfda5a4f Mon Sep 17 00:00:00 2001 From: Richard Cheng Date: Wed, 24 Jun 2026 22:41:47 +0800 Subject: [PATCH] cxl/mbox: Clamp mailbox output allocation to the payload size CXL_MEM_SEND_COMMAND bounds the user's in.size to the mailbox payload size but leaves out.size unbounded, then cxl_mbox_cmd_ctor() calls kvzalloc(out.size). A large out.size drives a huge allocation, above INT_MAX it WARNs and taints, and with panic_on_warn=1 it panics. The transport __cxl_pci_mbox_send_cmd() already clamps the response copy to min(out.size, payload_size, device len), so the output buffer is never written beyond payload_size. Clamp the allocation to payload_size too, matching the RAW path. Fixes: 583fa5e71cae ("cxl/mem: Add basic IOCTL interface") Reviewed-by: Kai-Heng Feng Reviewed-by: Koba Ko Reviewed-by: Dave Jiang Reviewed-by: Davidlohr Bueso Signed-off-by: Richard Cheng Link: https://patch.msgid.link/20260624144147.53997-1-icheng@nvidia.com Signed-off-by: Dave Jiang --- drivers/cxl/core/mbox.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c index 7c6c5b7450a5..d9cb02c9f72c 100644 --- a/drivers/cxl/core/mbox.c +++ b/drivers/cxl/core/mbox.c @@ -380,11 +380,7 @@ static int cxl_mbox_cmd_ctor(struct cxl_mbox_cmd *mbox_cmd, } } - /* Prepare to handle a full payload for variable sized output */ - if (out_size == CXL_VARIABLE_PAYLOAD) - mbox_cmd->size_out = cxl_mbox->payload_size; - else - mbox_cmd->size_out = out_size; + mbox_cmd->size_out = min_t(size_t, out_size, cxl_mbox->payload_size); if (mbox_cmd->size_out) { mbox_cmd->payload_out = kvzalloc(mbox_cmd->size_out, GFP_KERNEL);