2022-01-21 21:18:19

by Miaoqian Lin

Subject: [PATCH] RDMA/rtrs: Fix double free in alloc_clt

Callback function rtrs_clt_dev_release() in put_device()
calls kfree(clt); to free memory. We shouldn't call kfree(clt) again.

Fixes: 6a98d71daea1 ("RDMA/rtrs: client: main functionality")
Signed-off-by: Miaoqian Lin <[email protected]>
---
drivers/infiniband/ulp/rtrs/rtrs-clt.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
index 7c3f98e57889..61723f48fbd4 100644
--- a/drivers/infiniband/ulp/rtrs/rtrs-clt.c
+++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
@@ -2741,7 +2741,7 @@ static struct rtrs_clt_sess *alloc_clt(const char *sessname, size_t paths_num,
err = device_register(&clt->dev);
if (err) {
put_device(&clt->dev);
- goto err;
+ goto err_free_cpu;
}

clt->kobj_paths = kobject_create_and_add("paths", &clt->dev.kobj);
@@ -2764,6 +2764,9 @@ static struct rtrs_clt_sess *alloc_clt(const char *sessname, size_t paths_num,
err:
free_percpu(clt->pcpu_path);
kfree(clt);
+ clt->pcpu_path = NULL;
+err_free_cpu:
+ free_percpu(clt->pcpu_path);
return ERR_PTR(err);
}

--
2.17.1

2022-01-21 22:13:35

by Jinpu Wang

Subject: Re: [PATCH] RDMA/rtrs: Fix double free in alloc_clt

On Thu, Jan 20, 2022 at 11:37 AM Miaoqian Lin <[email protected]> wrote:
>
> Callback function rtrs_clt_dev_release() in put_device()
> calls kfree(clt); to free memory. We shouldn't call kfree(clt) again.
>
right, there is a bug, but the fix is not right.
> Fixes: 6a98d71daea1 ("RDMA/rtrs: client: main functionality")
> Signed-off-by: Miaoqian Lin <[email protected]>
> ---
> drivers/infiniband/ulp/rtrs/rtrs-clt.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
> index 7c3f98e57889..61723f48fbd4 100644
> --- a/drivers/infiniband/ulp/rtrs/rtrs-clt.c
> +++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
> @@ -2741,7 +2741,7 @@ static struct rtrs_clt_sess *alloc_clt(const char *sessname, size_t paths_num,
> err = device_register(&clt->dev);
> if (err) {
> put_device(&clt->dev);
> - goto err;
> + goto err_free_cpu;
> }
>
> clt->kobj_paths = kobject_create_and_add("paths", &clt->dev.kobj);
> @@ -2764,6 +2764,9 @@ static struct rtrs_clt_sess *alloc_clt(const char *sessname, size_t paths_num,
> err:
> free_percpu(clt->pcpu_path);
> kfree(clt);
> + clt->pcpu_path = NULL;
> +err_free_cpu:
> + free_percpu(clt->pcpu_path);
this still lead to use after free, because clt could be free already.
the right fix should move the free_percpu() to the release call back
before kfree(clt);
> return ERR_PTR(err);
> }
>
> --
> 2.17.1
>

2022-01-24 08:03:48

by Leon Romanovsky

Subject: Re: [PATCH] RDMA/rtrs: Fix double free in alloc_clt

On Thu, Jan 20, 2022 at 10:37:14AM +0000, Miaoqian Lin wrote:
> Callback function rtrs_clt_dev_release() in put_device()
> calls kfree(clt); to free memory. We shouldn't call kfree(clt) again.
>
> Fixes: 6a98d71daea1 ("RDMA/rtrs: client: main functionality")
> Signed-off-by: Miaoqian Lin <[email protected]>
> ---
> drivers/infiniband/ulp/rtrs/rtrs-clt.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
> index 7c3f98e57889..61723f48fbd4 100644
> --- a/drivers/infiniband/ulp/rtrs/rtrs-clt.c
> +++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
> @@ -2741,7 +2741,7 @@ static struct rtrs_clt_sess *alloc_clt(const char *sessname, size_t paths_num,
> err = device_register(&clt->dev);
> if (err) {
> put_device(&clt->dev);
> - goto err;
> + goto err_free_cpu;
> }
>
> clt->kobj_paths = kobject_create_and_add("paths", &clt->dev.kobj);
> @@ -2764,6 +2764,9 @@ static struct rtrs_clt_sess *alloc_clt(const char *sessname, size_t paths_num,
> err:
> free_percpu(clt->pcpu_path);
> kfree(clt);
> + clt->pcpu_path = NULL;

Like Jinpu said, it will crash, you are trying to access clt after kfree.

Thanks

> +err_free_cpu:
> + free_percpu(clt->pcpu_path);
> return ERR_PTR(err);
> }
>
> --
> 2.17.1
>