[rds,linux-next,2/2] net/rds: remove user triggered WARN_ON in rds_sendmsg

Commit Message

Shamir Rabinovitch Dec. 10, 2018, 7:53 a.m. UTC

From: shamir rabinovitch <[e-mail]>

per comment from Leon in rdma mailing list
https://lkml.org/lkml/2018/10/31/312 :

Please don't forget to remove user triggered WARN_ON.
https://lwn.net/Articles/769365/
"Greg Kroah-Hartman raised the problem of core kernel API code that will
use WARN_ON_ONCE() to complain about bad usage; that will not generate
the desired result if WARN_ON_ONCE() is configured to crash the machine.
He was told that the code should just call pr_warn() instead, and that
the called function should return an error in such situations. It was
generally agreed that any WARN_ON() or WARN_ON_ONCE() calls that can be
triggered from user space need to be fixed."

Suggested-by: Leon Romanovsky <[e-mail]>
Acked-by: Santosh Shilimkar <[e-mail]>
Signed-off-by: shamir rabinovitch <[e-mail]>
---
 net/rds/message.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Patch

diff --git a/net/rds/message.c b/net/rds/message.c
index 4b00b1152a5f..c28ad4b111af 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -313,11 +313,14 @@  struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents)
 	struct scatterlist *sg_first = (struct scatterlist *) &rm[1];
 	struct scatterlist *sg_ret;
 
-	WARN_ON(rm->m_used_sgs + nents > rm->m_total_sgs);
-	WARN_ON(!nents);
-
-	if (rm->m_used_sgs + nents > rm->m_total_sgs)
+	if (rm->m_used_sgs + nents > rm->m_total_sgs) {
+		pr_warn("rds: alloc sgs failed! total %d used %d nents %d\n",
+			rm->m_total_sgs, rm->m_used_sgs, nents);
 		return NULL;
+	}
+
+	if (!nents)
+		pr_warn("rds: alloc sgs failed! nents 0\n");
 
 	sg_ret = &sg_first[rm->m_used_sgs];
 	sg_init_table(sg_ret, nents);