2018-11-13 09:32:05

by Colin King

Subject: [PATCH][bpf-next] bpf: fix null pointer dereference on pointer offload

From: Colin Ian King <[email protected]>

Pointer offload is being null checked however the following statement
dereferences the potentially null pointer offload when assigning
offload->dev_state. Fix this by only assigning it if offload is not
null.

Detected by CoverityScan, CID#1475437 ("Dereference after null check")

Fixes: 00db12c3d141 ("bpf: call verifier_prep from its callback in struct bpf_offload_dev")
Signed-off-by: Colin Ian King <[email protected]>
---
kernel/bpf/offload.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index 52c5617e3716..54cf2b9c44a4 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -130,9 +130,10 @@ int bpf_prog_offload_verifier_prep(struct bpf_prog *prog)

down_read(&bpf_devs_lock);
offload = prog->aux->offload;
- if (offload)
+ if (offload) {
ret = offload->offdev->ops->prepare(prog);
- offload->dev_state = !ret;
+ offload->dev_state = !ret;
+ }
up_read(&bpf_devs_lock);

return ret;
--
2.19.1

2018-11-15 00:54:00

by Jakub Kicinski

Subject: Re: [PATCH][bpf-next] bpf: fix null pointer dereference on pointer offload

On Tue, 13 Nov 2018 09:29:26 +0000, Colin King wrote:
> From: Colin Ian King <[email protected]>
>
> Pointer offload is being null checked however the following statement
> dereferences the potentially null pointer offload when assigning
> offload->dev_state. Fix this by only assigning it if offload is not
> null.
>
> Detected by CoverityScan, CID#1475437 ("Dereference after null check")
>
> Fixes: 00db12c3d141 ("bpf: call verifier_prep from its callback in struct bpf_offload_dev")
> Signed-off-by: Colin Ian King <[email protected]>

Acked-by: Jakub Kicinski <[email protected]>

Thanks!

2018-11-17 04:53:37

by Alexei Starovoitov

Subject: Re: [PATCH][bpf-next] bpf: fix null pointer dereference on pointer offload

On Tue, Nov 13, 2018 at 09:29:26AM +0000, Colin King wrote:
> From: Colin Ian King <[email protected]>
>
> Pointer offload is being null checked however the following statement
> dereferences the potentially null pointer offload when assigning
> offload->dev_state. Fix this by only assigning it if offload is not
> null.
>
> Detected by CoverityScan, CID#1475437 ("Dereference after null check")
>
> Fixes: 00db12c3d141 ("bpf: call verifier_prep from its callback in struct bpf_offload_dev")
> Signed-off-by: Colin Ian King <[email protected]>

Applied, Thanks