net/rds: remove user triggered WARN_ON in rds_sendmsg
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."
in addition harden rds_sendmsg to detect and overcome issues with
invalid sg count and fail the sendmsg.
Suggested-by: Leon Romanovsky <leon@kernel.org>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: shamir rabinovitch <shamir.rabinovitch@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/rds/rds.h b/net/rds/rds.h
index 4d25231..02ec4a3 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -839,7 +839,8 @@ rds_conn_connecting(struct rds_connection *conn)
/* message.c */
struct rds_message *rds_message_alloc(unsigned int nents, gfp_t gfp);
-struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents);
+struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents,
+ int *ret);
int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
bool zcopy);
struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned int total_len);