2021-08-05 17:38:31

by Tuo Li

Subject: [PATCH] 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, if memory allocation
for m->m_info fails, free m and return -ENOMEM.

Reported-by: TOTE Robot <[email protected]>
Signed-off-by: Tuo Li <[email protected]>
---
fs/ceph/mdsmap.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
index abd9af7727ad..7d73e4b64b12 100644
--- a/fs/ceph/mdsmap.c
+++ b/fs/ceph/mdsmap.c
@@ -166,8 +166,10 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
m->possible_max_rank = max(m->m_num_active_mds, m->m_max_mds);

m->m_info = kcalloc(m->possible_max_rank, sizeof(*m->m_info), GFP_NOFS);
- if (!m->m_info)
- goto nomem;
+ if (!m->m_info) {
+ kfree(m);
+ return ERR_PTR(-ENOMEM);
+ }

/* pick out active nodes from mds_info (state > 0) */
for (i = 0; i < n; i++) {
--
2.25.1

2021-08-05 17:44:23

by Jeffrey Layton

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

On Thu, 2021-08-05 at 05:20 -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, if memory allocation
> for m->m_info fails, free m and return -ENOMEM.
>
> Reported-by: TOTE Robot <[email protected]>
> Signed-off-by: Tuo Li <[email protected]>
> ---
> fs/ceph/mdsmap.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
> index abd9af7727ad..7d73e4b64b12 100644
> --- a/fs/ceph/mdsmap.c
> +++ b/fs/ceph/mdsmap.c
> @@ -166,8 +166,10 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
> m->possible_max_rank = max(m->m_num_active_mds, m->m_max_mds);
>
> m->m_info = kcalloc(m->possible_max_rank, sizeof(*m->m_info), GFP_NOFS);
> - if (!m->m_info)
> - goto nomem;
> + if (!m->m_info) {
> + kfree(m);
> + return ERR_PTR(-ENOMEM);
> + }
>
> /* pick out active nodes from mds_info (state > 0) */
> for (i = 0; i < n; i++) {

Good catch. This function is already pretty complex. How about we
instead fix this in ceph_mdsmap_destroy and make it safe to call that
with the mdsmap in this state?

Basically, just put an "if (m->m_info)" around the for loop in that
function. Sound ok?

--
Jeff Layton <[email protected]>

2021-08-05 17:47:58

by Tuo Li

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

Thanks for your feedback. It sounds good to put an "if (m->m_info)" around
the for loop to fix this bug, as well as avoid other potential bugs
caused by calling
ceph_mdsmap_destroy(). I think we can prepare a V2 patch according to
your advice.


On 2021/8/5 20:29, Jeff Layton wrote:
> On Thu, 2021-08-05 at 05:20 -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, if memory allocation
>> for m->m_info fails, free m and return -ENOMEM.
>>
>> Reported-by: TOTE Robot <[email protected]>
>> Signed-off-by: Tuo Li <[email protected]>
>> ---
>> fs/ceph/mdsmap.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
>> index abd9af7727ad..7d73e4b64b12 100644
>> --- a/fs/ceph/mdsmap.c
>> +++ b/fs/ceph/mdsmap.c
>> @@ -166,8 +166,10 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
>> m->possible_max_rank = max(m->m_num_active_mds, m->m_max_mds);
>>
>> m->m_info = kcalloc(m->possible_max_rank, sizeof(*m->m_info), GFP_NOFS);
>> - if (!m->m_info)
>> - goto nomem;
>> + if (!m->m_info) {
>> + kfree(m);
>> + return ERR_PTR(-ENOMEM);
>> + }
>>
>> /* pick out active nodes from mds_info (state > 0) */
>> for (i = 0; i < n; i++) {
> Good catch. This function is already pretty complex. How about we
> instead fix this in ceph_mdsmap_destroy and make it safe to call that
> with the mdsmap in this state?
>
> Basically, just put an "if (m->m_info)" around the for loop in that
> function. Sound ok?
>