2017-12-22 17:51:53

by Colin King

Subject: [PATCH] tee: shm: don't put_page on null shm->pages

From: Colin Ian King <[email protected]>

In the case that shm->pages fails to allocate, the current exit
error path will try to put_page on a null shm->pages and cause
a null pointer dereference when accessing shm->pages[n]. Fix this
by only performing the put_page and kfree on shm->pages if it
is not null.

Detected by CoverityScan, CID#1463283 ("Dereference after null check")

Fixes: 033ddf12bcf5 ("tee: add register user memory")
Signed-off-by: Colin Ian King <[email protected]>
---
drivers/tee/tee_shm.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 13b4de1157c7..6890c8aaef8c 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -335,9 +335,11 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
idr_remove(&teedev->idr, shm->id);
mutex_unlock(&teedev->mutex);
}
- for (n = 0; n < shm->num_pages; n++)
- put_page(shm->pages[n]);
- kfree(shm->pages);
+ if (shm->pages) {
+ for (n = 0; n < shm->num_pages; n++)
+ put_page(shm->pages[n]);
+ kfree(shm->pages);
+ }
}
kfree(shm);
teedev_ctx_put(ctx);
--
2.14.1

2017-12-28 21:10:32

by Jens Wiklander

Subject: Re: [PATCH] tee: shm: don't put_page on null shm->pages

On Fri, Dec 22, 2017 at 6:51 PM, Colin King <[email protected]> wrote:
> From: Colin Ian King <[email protected]>
>
> In the case that shm->pages fails to allocate, the current exit
> error path will try to put_page on a null shm->pages and cause
> a null pointer dereference when accessing shm->pages[n]. Fix this
> by only performing the put_page and kfree on shm->pages if it
> is not null.
>
> Detected by CoverityScan, CID#1463283 ("Dereference after null check")
>
> Fixes: 033ddf12bcf5 ("tee: add register user memory")
> Signed-off-by: Colin Ian King <[email protected]>
> ---
> drivers/tee/tee_shm.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> index 13b4de1157c7..6890c8aaef8c 100644
> --- a/drivers/tee/tee_shm.c
> +++ b/drivers/tee/tee_shm.c
> @@ -335,9 +335,11 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
> idr_remove(&teedev->idr, shm->id);
> mutex_unlock(&teedev->mutex);
> }
> - for (n = 0; n < shm->num_pages; n++)
> - put_page(shm->pages[n]);
> - kfree(shm->pages);
> + if (shm->pages) {
> + for (n = 0; n < shm->num_pages; n++)
> + put_page(shm->pages[n]);
> + kfree(shm->pages);
> + }
> }
> kfree(shm);
> teedev_ctx_put(ctx);
> --
> 2.14.1
>

Looks good. Thanks.

/Jens