2017-04-25 06:50:04

by Heloise

Subject: [PATCH] drivers:block:drbd:drbd_state:fix null-pointer dereference

Signed-off-by: Heloise <[email protected]>

In is_valid_state(), there is NULL validation for the variable nc
"if (nc)". However,the code will continue to execute when nc is NULL.
nc->verify_alg[0] is used in subsequent code, which may cause
null-pointer dereference, fix it.
---
drivers/block/drbd/drbd_state.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index eea0c4a..1963b83 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c
@@ -845,7 +845,7 @@ is_valid_state(struct drbd_device *device, union drbd_state ns)
rv = SS_CONNECTED_OUTDATES;

else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
- (nc->verify_alg[0] == 0))
+ (nc != NULL && nc->verify_alg[0] == 0))
rv = SS_NO_VERIFY_ALG;

else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
--
2.1.0

2017-04-25 07:06:12

by Lars Ellenberg

Subject: Re: [PATCH] drivers:block:drbd:drbd_state:fix null-pointer dereference

On Mon, Apr 24, 2017 at 11:35:18PM -0700, Heloise wrote:
> Signed-off-by: Heloise <[email protected]>
>
> In is_valid_state(), there is NULL validation for the variable nc
> "if (nc)". However,the code will continue to execute when nc is NULL.
> nc->verify_alg[0] is used in subsequent code, which may cause
> null-pointer dereference, fix it.
> ---
> drivers/block/drbd/drbd_state.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
> index eea0c4a..1963b83 100644
> --- a/drivers/block/drbd/drbd_state.c
> +++ b/drivers/block/drbd/drbd_state.c
> @@ -845,7 +845,7 @@ is_valid_state(struct drbd_device *device, union drbd_state ns)
> rv = SS_CONNECTED_OUTDATES;
>
> else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
> - (nc->verify_alg[0] == 0))
> + (nc != NULL && nc->verify_alg[0] == 0))


What the static checker cannot know:
ns.conn != C_STANDALONE implies nc != NULL.

But if you feel like it, the additional check won't hurt.

Thanks,

Lars