[PATCH 6.12 160/244] scsi: ibmvfc: Fix OOB access in ibmvfc_discover_targets_done()

Greg Kroah-Hartman
2026-03-31T16:52:59Z

From: Tyllis Xu <livelycarpet87@gmail.com>

commit 61d099ac4a7a8fb11ebdb6e2ec8d77f38e77362f upstream.

A malicious or compromised VIO server can return a num_written value in the
discover targets MAD response that exceeds max_targets. This value is
stored directly in vhost->num_targets without validation, and is then used
as the loop bound in ibmvfc_alloc_targets() to index into disc_buf[], which
is only allocated for max_targets entries. Indices at or beyond max_targets
access kernel memory outside the DMA-coherent allocation. The
out-of-bounds data is subsequently embedded in Implicit Logout and PLOGI
MADs that are sent back to the VIO server, leaking kernel memory.

Fix by clamping num_written to max_targets before storing it.

Fixes: 072b91f9c651 ("[SCSI] ibmvfc: IBM Power Virtual Fibre Channel Adapter Client Driver")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Tyllis Xu <LivelyCarpet87@gmail.com>
Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com>
Acked-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Link: https://patch.msgid.link/20260314170151.548614-1-LivelyCarpet87@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/scsi/ibmvscsi/ibmvfc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/scsi/ibmvscsi/ibmvfc.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc.c
@@ -4963,7 +4963,8 @@ static void ibmvfc_discover_targets_done
switch (mad_status) {
case IBMVFC_MAD_SUCCESS:
ibmvfc_dbg(vhost, "Discover Targets succeeded\n");
- vhost->num_targets = be32_to_cpu(rsp->num_written);
+ vhost->num_targets = min_t(u32, be32_to_cpu(rsp->num_written),
+ max_targets);
ibmvfc_set_host_action(vhost, IBMVFC_HOST_ACTION_ALLOC_TGTS);
break;