2021-08-05 18:59:01

by Tuo Li

Subject: [PATCH v2] ceph: fix possible null-pointer dereference in ceph_mdsmap_decode()

kcalloc() is called to allocate memory for m->m_info, and if it fails,
ceph_mdsmap_destroy() behind the label out_err will be called:
ceph_mdsmap_destroy(m);

In ceph_mdsmap_destroy(), m->m_info is dereferenced through:
kfree(m->m_info[i].export_targets);

To fix this possible null-pointer dereference, check m->m_info before the
for loop to free m->m_info[i].export_targets.

Reported-by: TOTE Robot <[email protected]>
Signed-off-by: Tuo Li <[email protected]>
---
v2:
* Put an "if (m->m_info)" around the for loop in ceph_mdsmap_destroy()
instead of freeing m and returning -ENOMEM in ceph_mdsmap_decode().
Thank Jeff Layton for helpful advice.
---
fs/ceph/mdsmap.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
index abd9af7727ad..26d6fa049b44 100644
--- a/fs/ceph/mdsmap.c
+++ b/fs/ceph/mdsmap.c
@@ -393,9 +393,11 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
void ceph_mdsmap_destroy(struct ceph_mdsmap *m)
{
int i;
-
- for (i = 0; i < m->possible_max_rank; i++)
- kfree(m->m_info[i].export_targets);
+
+ if (m->m_info) {
+ for (i = 0; i < m->possible_max_rank; i++)
+ kfree(m->m_info[i].export_targets);
+ }
kfree(m->m_info);
kfree(m->m_data_pg_pools);
kfree(m);
--
2.25.1

2021-08-05 21:19:06

by Jeffrey Layton

Subject: Re: [PATCH v2] ceph: fix possible null-pointer dereference in ceph_mdsmap_decode()

On Thu, 2021-08-05 at 08:14 -0700, Tuo Li wrote:
> kcalloc() is called to allocate memory for m->m_info, and if it fails,
> ceph_mdsmap_destroy() behind the label out_err will be called:
> ceph_mdsmap_destroy(m);
>
> In ceph_mdsmap_destroy(), m->m_info is dereferenced through:
> kfree(m->m_info[i].export_targets);
>
> To fix this possible null-pointer dereference, check m->m_info before the
> for loop to free m->m_info[i].export_targets.
>
> Reported-by: TOTE Robot <[email protected]>
> Signed-off-by: Tuo Li <[email protected]>
> ---
> v2:
> * Put an "if (m->m_info)" around the for loop in ceph_mdsmap_destroy()
> instead of freeing m and returning -ENOMEM in ceph_mdsmap_decode().
> Thank Jeff Layton for helpful advice.
> ---
> fs/ceph/mdsmap.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
> index abd9af7727ad..26d6fa049b44 100644
> --- a/fs/ceph/mdsmap.c
> +++ b/fs/ceph/mdsmap.c
> @@ -393,9 +393,11 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
> void ceph_mdsmap_destroy(struct ceph_mdsmap *m)
> {
> int i;
> -
> - for (i = 0; i < m->possible_max_rank; i++)
> - kfree(m->m_info[i].export_targets);
> +

This patch added some whitespace damage above. I went ahead and fixed it
up before merging.

> + if (m->m_info) {
> + for (i = 0; i < m->possible_max_rank; i++)
> + kfree(m->m_info[i].export_targets);
> + }
> kfree(m->m_info);

I also moved the above kfree into the if statement since we have to
check it anyway (no need to do it twice).

> kfree(m->m_data_pg_pools);
> kfree(m);

Merged! Thanks for the patch.
--
Jeff Layton <[email protected]>