cifs: fix memory leak of an allocated cifs_ntsd structure

Message ID 20190107171515.4537-1-colin.king@canonical.com
State New
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Series
  • cifs: fix memory leak of an allocated cifs_ntsd structure
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Commit Message

Colin King Jan. 7, 2019, 5:15 p.m.
From: Colin Ian King <colin.king@canonical.com>

The call to SMB2_queary_acl can allocate memory to pntsd and also
return a failure via a call to SMB2_query_acl (and then query_info).
This occurs when query_info allocates the structure and then in
query_info the call to smb2_validate_and_copy_iov fails. Currently the
failure just returns without kfree'ing pntsd hence causing a memory
leak.  Fix this by kfree'ing pntsd before returning.

Detected by CoverityScan, CID#1457059 ("Resource Leak")

Fixes: 2f1afe25997f ("cifs: Use smb 2 - 3 and cifsacl mount options getacl functions")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 fs/cifs/smb2ops.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Dan Carpenter Jan. 8, 2019, 9:42 a.m. | #1
On Mon, Jan 07, 2019 at 05:15:15PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The call to SMB2_queary_acl can allocate memory to pntsd and also
> return a failure via a call to SMB2_query_acl (and then query_info).
> This occurs when query_info allocates the structure and then in
> query_info the call to smb2_validate_and_copy_iov fails. Currently the
> failure just returns without kfree'ing pntsd hence causing a memory
> leak.  Fix this by kfree'ing pntsd before returning.
> 
> Detected by CoverityScan, CID#1457059 ("Resource Leak")
> 
> Fixes: 2f1afe25997f ("cifs: Use smb 2 - 3 and cifsacl mount options getacl functions")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  fs/cifs/smb2ops.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index cf7eb891804f..6d71958ad2cb 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -2238,8 +2238,10 @@ get_smb2_acl_by_fid(struct cifs_sb_info *cifs_sb,
>  	cifs_put_tlink(tlink);
>  
>  	cifs_dbg(FYI, "%s: rc = %d ACL len %d\n", __func__, rc, *pacllen);
> -	if (rc)
> +	if (rc) {
> +		kfree(pntsd);
>  		return ERR_PTR(rc);
> +	}

This is a layering violation.  The memory was allocated in query_info()
so it should be freed there instead.  Also if the kmalloc() fails in
query_info() then it should return -ENOMEM instead of success.

This only affects code which calls SMB2_query_acl().  There are two
callers.  You have fixed one but the other is also buggy because we're
returning uninitialized memory in get_smb2_acl_by_path().

regards,
dan carpenter
Colin King Jan. 8, 2019, 9:49 a.m. | #2
On 08/01/2019 09:42, Dan Carpenter wrote:
> On Mon, Jan 07, 2019 at 05:15:15PM +0000, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> The call to SMB2_queary_acl can allocate memory to pntsd and also
>> return a failure via a call to SMB2_query_acl (and then query_info).
>> This occurs when query_info allocates the structure and then in
>> query_info the call to smb2_validate_and_copy_iov fails. Currently the
>> failure just returns without kfree'ing pntsd hence causing a memory
>> leak.  Fix this by kfree'ing pntsd before returning.
>>
>> Detected by CoverityScan, CID#1457059 ("Resource Leak")
>>
>> Fixes: 2f1afe25997f ("cifs: Use smb 2 - 3 and cifsacl mount options getacl functions")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>  fs/cifs/smb2ops.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
>> index cf7eb891804f..6d71958ad2cb 100644
>> --- a/fs/cifs/smb2ops.c
>> +++ b/fs/cifs/smb2ops.c
>> @@ -2238,8 +2238,10 @@ get_smb2_acl_by_fid(struct cifs_sb_info *cifs_sb,
>>  	cifs_put_tlink(tlink);
>>  
>>  	cifs_dbg(FYI, "%s: rc = %d ACL len %d\n", __func__, rc, *pacllen);
>> -	if (rc)
>> +	if (rc) {
>> +		kfree(pntsd);
>>  		return ERR_PTR(rc);
>> +	}
> 
> This is a layering violation.  The memory was allocated in query_info()
> so it should be freed there instead.  Also if the kmalloc() fails in
> query_info() then it should return -ENOMEM instead of success.
> 
> This only affects code which calls SMB2_query_acl().  There are two
> callers.  You have fixed one but the other is also buggy because we're
> returning uninitialized memory in get_smb2_acl_by_path().
> 
> regards,
> dan carpenter
> 

Eep. very true. NACK to my fixes and I'll sort out a correct fix later.

Colin
Steve French Jan. 8, 2019, 5:46 p.m. | #3
Yes - good point.  Will back this out temporarily, and also update
Aurelien's (unrelated patch) to the later version

On Tue, Jan 8, 2019 at 3:52 AM Colin Ian King <colin.king@canonical.com> wrote:
>
> On 08/01/2019 09:42, Dan Carpenter wrote:
> > On Mon, Jan 07, 2019 at 05:15:15PM +0000, Colin King wrote:
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> The call to SMB2_queary_acl can allocate memory to pntsd and also
> >> return a failure via a call to SMB2_query_acl (and then query_info).
> >> This occurs when query_info allocates the structure and then in
> >> query_info the call to smb2_validate_and_copy_iov fails. Currently the
> >> failure just returns without kfree'ing pntsd hence causing a memory
> >> leak.  Fix this by kfree'ing pntsd before returning.
> >>
> >> Detected by CoverityScan, CID#1457059 ("Resource Leak")
> >>
> >> Fixes: 2f1afe25997f ("cifs: Use smb 2 - 3 and cifsacl mount options getacl functions")
> >> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >> ---
> >>  fs/cifs/smb2ops.c | 4 +++-
> >>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> >> index cf7eb891804f..6d71958ad2cb 100644
> >> --- a/fs/cifs/smb2ops.c
> >> +++ b/fs/cifs/smb2ops.c
> >> @@ -2238,8 +2238,10 @@ get_smb2_acl_by_fid(struct cifs_sb_info *cifs_sb,
> >>      cifs_put_tlink(tlink);
> >>
> >>      cifs_dbg(FYI, "%s: rc = %d ACL len %d\n", __func__, rc, *pacllen);
> >> -    if (rc)
> >> +    if (rc) {
> >> +            kfree(pntsd);
> >>              return ERR_PTR(rc);
> >> +    }
> >
> > This is a layering violation.  The memory was allocated in query_info()
> > so it should be freed there instead.  Also if the kmalloc() fails in
> > query_info() then it should return -ENOMEM instead of success.
> >
> > This only affects code which calls SMB2_query_acl().  There are two
> > callers.  You have fixed one but the other is also buggy because we're
> > returning uninitialized memory in get_smb2_acl_by_path().
> >
> > regards,
> > dan carpenter
> >
>
> Eep. very true. NACK to my fixes and I'll sort out a correct fix later.
>
> Colin

Patch

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index cf7eb891804f..6d71958ad2cb 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2238,8 +2238,10 @@  get_smb2_acl_by_fid(struct cifs_sb_info *cifs_sb,
 	cifs_put_tlink(tlink);
 
 	cifs_dbg(FYI, "%s: rc = %d ACL len %d\n", __func__, rc, *pacllen);
-	if (rc)
+	if (rc) {
+		kfree(pntsd);
 		return ERR_PTR(rc);
+	}
 	return pntsd;
 
 }