[PATCH 5.11 148/210] net/rds: Fix a use after free in rds_message_map_pages

Greg Kroah-Hartman
2021-04-12T09:35:17Z

From: Lv Yunlong <lyl2019@mail.ustc.edu.cn>

[ Upstream commit bdc2ab5c61a5c07388f4820ff21e787b4dfd1ced ]

In rds_message_map_pages, the rm is freed by rds_message_put(rm).
But rm is still used by rm->data.op_sg in return value.

My patch assigns ERR_CAST(rm->data.op_sg) to err before the rm is
freed to avoid the uaf.

Fixes: 7dba92037baf3 ("net/rds: Use ERR_PTR for rds_message_alloc_sgs()")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/rds/message.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/rds/message.c b/net/rds/message.c
index 071a261fdaab..799034e0f513 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -347,8 +347,9 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
rm->data.op_nents = DIV_ROUND_UP(total_len, PAGE_SIZE);
rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
if (IS_ERR(rm->data.op_sg)) {
+ void *err = ERR_CAST(rm->data.op_sg);
rds_message_put(rm);
- return ERR_CAST(rm->data.op_sg);
+ return err;
}

for (i = 0; i < rm->data.op_nents; ++i) {
--
2.30.2