2021-03-31 02:02:13

by Lv Yunlong

Subject: [PATCH v2] 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 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 <[email protected]>
---
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) {
--
2.25.1

2021-03-31 18:30:22

by Håkon Bugge

Subject: Re: [PATCH v2] net/rds: Fix a use after free in rds_message_map_pages

> On 31 Mar 2021, at 03:59, Lv Yunlong <[email protected]> wrote:
>
> 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 <[email protected]>

Reviewed-by: Håkon Bugge <[email protected]>


Thanks for fixing this:-)

Håkon


> ---
> 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) {
> --
> 2.25.1
>
>

2021-03-31 21:42:47

by patchwork-bot+netdevbpf

Subject: Re: [PATCH v2] net/rds: Fix a use after free in rds_message_map_pages

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Tue, 30 Mar 2021 18:59:59 -0700 you wrote:
> 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 <[email protected]>
>
> [...]

Here is the summary with links:
- [v2] net/rds: Fix a use after free in rds_message_map_pages
https://git.kernel.org/netdev/net/c/bdc2ab5c61a5

You are awesome, thank you!
--
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