IB/srp: Enforce protocol limit on srp_sg_tablesize

The current SRP initiator will allow unlimited s/g entries in the
indirect descriptors lists, but the entry count field in the SRP_CMD
request is 8 bits, so setting srp_sg_tablesize too large will open the
possibility of wrapping the count and generating invalid requests.

Clamp srp_sg_tablesize to the protocol limits to prevent surprises.

Reported by Martin W. Schlining III <mschlining@datadirectnet.com>.

Signed-off-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index fd4a49fc4773..125765aa9d59 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -68,7 +68,7 @@ static int srp_max_iu_len;
 
 module_param(srp_sg_tablesize, int, 0444);
 MODULE_PARM_DESC(srp_sg_tablesize,
-                 "Max number of gather/scatter entries per I/O (default is 12)");
+                 "Max number of gather/scatter entries per I/O (default is 12, max 255)");
 
 static int topspin_workarounds = 1;
 
@@ -2138,6 +2138,11 @@ static int __init srp_init_module(void)
 {
         int ret;
 
+        if (srp_sg_tablesize > 255) {
+                printk(KERN_WARNING PFX "Clamping srp_sg_tablesize to 255\n");
+                srp_sg_tablesize = 255;
+        }
+
         ib_srp_transport_template =
                 srp_attach_transport(&ib_srp_transport_functions);
         if (!ib_srp_transport_template)