2021-03-30 10:18:17

by Lv Yunlong

Subject: [PATCH] net/rds: Fix a use after free in rds_message_map_pages

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 replaces ERR_CAST(rm->data.op_sg) to ERR_PTR(-ENOMEM) to avoid
the uaf.

Fixes: 7dba92037baf3 ("net/rds: Use ERR_PTR for rds_message_alloc_sgs()")
Signed-off-by: Lv Yunlong <[email protected]>
---
net/rds/message.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/message.c b/net/rds/message.c
index 071a261fdaab..cecd968c9b25 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -348,7 +348,7 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
if (IS_ERR(rm->data.op_sg)) {
rds_message_put(rm);
- return ERR_CAST(rm->data.op_sg);
+ return ERR_PTR(-ENOMEM);
}

for (i = 0; i < rm->data.op_nents; ++i) {
--
2.25.1

2021-03-31 00:06:55

by David Miller

Subject: Re: [PATCH] net/rds: Fix a use after free in rds_message_map_pages

From: Lv Yunlong <[email protected]>
Date: Tue, 30 Mar 2021 03:16:02 -0700

> @@ -348,7 +348,7 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
> rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
> if (IS_ERR(rm->data.op_sg)) {
> rds_message_put(rm);
> - return ERR_CAST(rm->data.op_sg);
> + return ERR_PTR(-ENOMEM);
> }
>
> for (i = 0; i < rm->data.op_nents; ++i) {

Maybe instead do:

int err = ERR_CAST(rm->data.op_sg);
rds_message_put(rm);
return err;

Then if rds_message_alloc_sgs() starts to return other errors, they will propagate.

Thank you.

2021-03-31 02:04:28

by Lv Yunlong

Subject: Re: Re: [PATCH] net/rds: Fix a use after free in rds_message_map_pages

> -----原始邮件-----
> 发件人: "David Miller" <[email protected]>
> 发送时间: 2021-03-31 08:02:28 (星期三)
> 收件人: [email protected]
> 抄送: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
> 主题: Re: [PATCH] net/rds: Fix a use after free in rds_message_map_pages
>
> From: Lv Yunlong <[email protected]>
> Date: Tue, 30 Mar 2021 03:16:02 -0700
>
> > @@ -348,7 +348,7 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
> > rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
> > if (IS_ERR(rm->data.op_sg)) {
> > rds_message_put(rm);
> > - return ERR_CAST(rm->data.op_sg);
> > + return ERR_PTR(-ENOMEM);
> > }
> >
> > for (i = 0; i < rm->data.op_nents; ++i) {
>
> Maybe instead do:
>
> int err = ERR_CAST(rm->data.op_sg);
> rds_message_put(rm);
> return err;
>
> Then if rds_message_alloc_sgs() starts to return other errors, they will propagate.
>
> Thank you.

The type of ERR_CAST() is void *, not int.
I think the correct patch is:

void *err = ERR_CAST(rm->data.op_sg);
rds_message_put(rm);
return err;

I have submitted the PATCH v2 for you to review.

Thanks.