[PATCH for-rc] RDMA/iwcm: Fix iwcm work deallocation

[PATCH for-rc] RDMA/iwcm: Fix iwcm work deallocation

[Bernard Metzler]

The dealloc_work_entries() function must update the
work_free_list pointer while freeing its entries, since
potentially called again on same list. A second iteration
of the work list caused system crash. This happens, if
work allocation fails during cma_iw_listen() and
free_cm_id() tries to free the list again during cleanup.

Reported-by: syzbot+cb0c054eabfba4342146@syzkaller.appspotmail.com
Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
---
 drivers/infiniband/core/iwcm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/iwcm.c b/drivers/infiniband/core/iwcm.c
index ade71823370f..da8adadf4755 100644
--- a/drivers/infiniband/core/iwcm.c
+++ b/drivers/infiniband/core/iwcm.c
@@ -159,8 +159,10 @@ static void dealloc_work_entries(struct iwcm_id_private *cm_id_priv)
 {
 	struct list_head *e, *tmp;
 
-	list_for_each_safe(e, tmp, &cm_id_priv->work_free_list)
+	list_for_each_safe(e, tmp, &cm_id_priv->work_free_list) {
+		list_del(e);
 		kfree(list_entry(e, struct iwcm_work, free_list));
+	}
 }
 
 static int alloc_work_entries(struct iwcm_id_private *cm_id_priv, int count)
-- 
2.17.2

Re: [PATCH for-rc] RDMA/iwcm: Fix iwcm work deallocation

[Jason Gunthorpe]

On Mon, Mar 02, 2020 at 07:16:14PM +0100, Bernard Metzler wrote:
> The dealloc_work_entries() function must update the
> work_free_list pointer while freeing its entries, since
> potentially called again on same list. A second iteration
> of the work list caused system crash. This happens, if
> work allocation fails during cma_iw_listen() and
> free_cm_id() tries to free the list again during cleanup.
> 
> Reported-by: syzbot+cb0c054eabfba4342146@syzkaller.appspotmail.com
> Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
> ---
>  drivers/infiniband/core/iwcm.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Applied to for-rc, please include Fixes lines in patches like this, I
added one
 
 diff --git a/drivers/infiniband/core/iwcm.c b/drivers/infiniband/core/iwcm.c
> index ade71823370f..da8adadf4755 100644
> --- a/drivers/infiniband/core/iwcm.c
> +++ b/drivers/infiniband/core/iwcm.c
> @@ -159,8 +159,10 @@ static void dealloc_work_entries(struct iwcm_id_private *cm_id_priv)
>  {
>  	struct list_head *e, *tmp;
>  
> -	list_for_each_safe(e, tmp, &cm_id_priv->work_free_list)
> +	list_for_each_safe(e, tmp, &cm_id_priv->work_free_list) {
> +		list_del(e);
>  		kfree(list_entry(e, struct iwcm_work, free_list));

It would be nice if someone were to fix the use of the list macros in
this file to use the _entry_ versions

Jason