smb: client: fix refcount leak in smb2_set_path_attr

[PATCH] smb: client: fix refcount leak in smb2_set_path_attr

Posted by Shuhao Fu 3 months ago

Fix refcount leak in `smb2_set_path_attr` when path conversion fails.

Function `cifs_get_writable_path` returns `cfile` with its reference
counter `cfile->count` increased on success. Function `smb2_compound_op`
would decrease the reference counter for `cfile`, as stated in its 
comment. By calling `smb2_rename_path`, the reference counter of `cfile`
would leak if `cifs_convert_path_to_utf16` fails in `smb2_set_path_attr`.

Fixes: 8de9e86c67ba ("cifs: create a helper to find a writeable handle by path name")
Signed-off-by: Shuhao Fu <sfual@cse.ust.hk>
---
 fs/smb/client/smb2inode.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
index 09e3fc81d..69cb81fa0 100644
--- a/fs/smb/client/smb2inode.c
+++ b/fs/smb/client/smb2inode.c
@@ -1294,6 +1294,8 @@ static int smb2_set_path_attr(const unsigned int xid, struct cifs_tcon *tcon,
 	smb2_to_name = cifs_convert_path_to_utf16(to_name, cifs_sb);
 	if (smb2_to_name == NULL) {
 		rc = -ENOMEM;
+		if (cfile)
+			cifsFileInfo_put(cfile);
 		goto smb2_rename_path;
 	}
 	in_iov.iov_base = smb2_to_name;
-- 
2.39.5 (Apple Git-154)

Re: [PATCH] smb: client: fix refcount leak in smb2_set_path_attr

Posted by Steve French 3 months ago

There are multiple callers - are there callers that don't call
"set_writeable_path()" ?    And so could cause the reverse refcount
issue?

On Tue, Nov 4, 2025 at 9:21 AM Shuhao Fu <sfual@cse.ust.hk> wrote:
>
> Fix refcount leak in `smb2_set_path_attr` when path conversion fails.
>
> Function `cifs_get_writable_path` returns `cfile` with its reference
> counter `cfile->count` increased on success. Function `smb2_compound_op`
> would decrease the reference counter for `cfile`, as stated in its
> comment. By calling `smb2_rename_path`, the reference counter of `cfile`
> would leak if `cifs_convert_path_to_utf16` fails in `smb2_set_path_attr`.
>
> Fixes: 8de9e86c67ba ("cifs: create a helper to find a writeable handle by path name")
> Signed-off-by: Shuhao Fu <sfual@cse.ust.hk>
> ---
>  fs/smb/client/smb2inode.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
> index 09e3fc81d..69cb81fa0 100644
> --- a/fs/smb/client/smb2inode.c
> +++ b/fs/smb/client/smb2inode.c
> @@ -1294,6 +1294,8 @@ static int smb2_set_path_attr(const unsigned int xid, struct cifs_tcon *tcon,
>         smb2_to_name = cifs_convert_path_to_utf16(to_name, cifs_sb);
>         if (smb2_to_name == NULL) {
>                 rc = -ENOMEM;
> +               if (cfile)
> +                       cifsFileInfo_put(cfile);
>                 goto smb2_rename_path;
>         }
>         in_iov.iov_base = smb2_to_name;
> --
> 2.39.5 (Apple Git-154)
>
>


-- 
Thanks,

Steve

Re: [PATCH] smb: client: fix refcount leak in smb2_set_path_attr

Posted by Shuhao Fu 3 months ago

On Tue, Nov 04, 2025 at 10:12:13AM -0600, Steve French wrote:
> There are multiple callers - are there callers that don't call
> "set_writeable_path()" ?    And so could cause the reverse refcount
> issue?

I found three calls to `smb2_set_path_attr`. Two in `smb2_rename_path`
and one in `smb2_create_hardlink`. The one in `smb2_create_hardlink`
passes NULL for cfile. Therefore, it would not cause reverse refcount
issue here.

Thanks,
Shuhao
> 
> On Tue, Nov 4, 2025 at 9:21 AM Shuhao Fu <sfual@cse.ust.hk> wrote:
> >
> > Fix refcount leak in `smb2_set_path_attr` when path conversion fails.
> >
> > Function `cifs_get_writable_path` returns `cfile` with its reference
> > counter `cfile->count` increased on success. Function `smb2_compound_op`
> > would decrease the reference counter for `cfile`, as stated in its
> > comment. By calling `smb2_rename_path`, the reference counter of `cfile`
> > would leak if `cifs_convert_path_to_utf16` fails in `smb2_set_path_attr`.
> >
> > Fixes: 8de9e86c67ba ("cifs: create a helper to find a writeable handle by path name")
> > Signed-off-by: Shuhao Fu <sfual@cse.ust.hk>
> > ---
> >  fs/smb/client/smb2inode.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
> > index 09e3fc81d..69cb81fa0 100644
> > --- a/fs/smb/client/smb2inode.c
> > +++ b/fs/smb/client/smb2inode.c
> > @@ -1294,6 +1294,8 @@ static int smb2_set_path_attr(const unsigned int xid, struct cifs_tcon *tcon,
> >         smb2_to_name = cifs_convert_path_to_utf16(to_name, cifs_sb);
> >         if (smb2_to_name == NULL) {
> >                 rc = -ENOMEM;
> > +               if (cfile)
> > +                       cifsFileInfo_put(cfile);
> >                 goto smb2_rename_path;
> >         }
> >         in_iov.iov_base = smb2_to_name;
> > --
> > 2.39.5 (Apple Git-154)
> >
> >
> 
> 
> -- 
> Thanks,
> 
> Steve

Re: [PATCH] smb: client: fix refcount leak in smb2_set_path_attr

Posted by Henrique Carvalho 3 months ago


On 11/4/25 1:12 PM, Steve French via samba-technical wrote:
> There are multiple callers - are there callers that don't call
> "set_writeable_path()" ?    And so could cause the reverse refcount
> issue?

Yes... Even if it does not cause an issue today, that fix looks like it
belongs inside smb2_rename_path?

> 
> On Tue, Nov 4, 2025 at 9:21 AM Shuhao Fu <sfual@cse.ust.hk> wrote:
>>
>> Fix refcount leak in `smb2_set_path_attr` when path conversion fails.
>>
>> Function `cifs_get_writable_path` returns `cfile` with its reference
>> counter `cfile->count` increased on success. Function `smb2_compound_op`
>> would decrease the reference counter for `cfile`, as stated in its
>> comment. By calling `smb2_rename_path`, the reference counter of `cfile`
>> would leak if `cifs_convert_path_to_utf16` fails in `smb2_set_path_attr`.
>>
>> Fixes: 8de9e86c67ba ("cifs: create a helper to find a writeable handle by path name")
>> Signed-off-by: Shuhao Fu <sfual@cse.ust.hk>
>> ---
>>  fs/smb/client/smb2inode.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
>> index 09e3fc81d..69cb81fa0 100644
>> --- a/fs/smb/client/smb2inode.c
>> +++ b/fs/smb/client/smb2inode.c
>> @@ -1294,6 +1294,8 @@ static int smb2_set_path_attr(const unsigned int xid, struct cifs_tcon *tcon,
>>         smb2_to_name = cifs_convert_path_to_utf16(to_name, cifs_sb);
>>         if (smb2_to_name == NULL) {
>>                 rc = -ENOMEM;
>> +               if (cfile)
>> +                       cifsFileInfo_put(cfile);
>>                 goto smb2_rename_path;
>>         }
>>         in_iov.iov_base = smb2_to_name;
>> --
>> 2.39.5 (Apple Git-154)
>>
>>
> 
> 

-- 
Henrique
SUSE Labs

Re: [PATCH] smb: client: fix refcount leak in smb2_set_path_attr

Posted by Shuhao Fu 3 months ago

On Tue, Nov 04, 2025 at 01:23:33PM -0300, Henrique Carvalho wrote:
> 
> 
> On 11/4/25 1:12 PM, Steve French via samba-technical wrote:
> > There are multiple callers - are there callers that don't call
> > "set_writeable_path()" ?    And so could cause the reverse refcount
> > issue?
> 
> Yes... Even if it does not cause an issue today, that fix looks like it
> belongs inside smb2_rename_path?

I placed decrement in `smb2_set_path_attr` since it seems like a wrapper
of `smb2_compound_op`. I figured that this wrapper should handle the
failure cases the same way as `smb2_compound_op`.

Thanks,
Shuhao
> 
> > 
> > On Tue, Nov 4, 2025 at 9:21 AM Shuhao Fu <sfual@cse.ust.hk> wrote:
> >>
> >> Fix refcount leak in `smb2_set_path_attr` when path conversion fails.
> >>
> >> Function `cifs_get_writable_path` returns `cfile` with its reference
> >> counter `cfile->count` increased on success. Function `smb2_compound_op`
> >> would decrease the reference counter for `cfile`, as stated in its
> >> comment. By calling `smb2_rename_path`, the reference counter of `cfile`
> >> would leak if `cifs_convert_path_to_utf16` fails in `smb2_set_path_attr`.
> >>
> >> Fixes: 8de9e86c67ba ("cifs: create a helper to find a writeable handle by path name")
> >> Signed-off-by: Shuhao Fu <sfual@cse.ust.hk>
> >> ---
> >>  fs/smb/client/smb2inode.c | 2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
> >> index 09e3fc81d..69cb81fa0 100644
> >> --- a/fs/smb/client/smb2inode.c
> >> +++ b/fs/smb/client/smb2inode.c
> >> @@ -1294,6 +1294,8 @@ static int smb2_set_path_attr(const unsigned int xid, struct cifs_tcon *tcon,
> >>         smb2_to_name = cifs_convert_path_to_utf16(to_name, cifs_sb);
> >>         if (smb2_to_name == NULL) {
> >>                 rc = -ENOMEM;
> >> +               if (cfile)
> >> +                       cifsFileInfo_put(cfile);
> >>                 goto smb2_rename_path;
> >>         }
> >>         in_iov.iov_base = smb2_to_name;
> >> --
> >> 2.39.5 (Apple Git-154)
> >>
> >>
> > 
> > 
> 
> -- 
> Henrique
> SUSE Labs

Re: [PATCH] smb: client: fix refcount leak in smb2_set_path_attr

Posted by Henrique Carvalho 3 months ago


On 11/4/25 1:56 PM, Shuhao Fu wrote:
> On Tue, Nov 04, 2025 at 01:23:33PM -0300, Henrique Carvalho wrote:
>>
>>
>> On 11/4/25 1:12 PM, Steve French via samba-technical wrote:
>>> There are multiple callers - are there callers that don't call
>>> "set_writeable_path()" ?    And so could cause the reverse refcount
>>> issue?
>>
>> Yes... Even if it does not cause an issue today, that fix looks like it
>> belongs inside smb2_rename_path?
> 
> I placed decrement in `smb2_set_path_attr` since it seems like a wrapper
> of `smb2_compound_op`. I figured that this wrapper should handle the
> failure cases the same way as `smb2_compound_op`.

Makes sense.

Acked-by: Henrique Carvalho <henrique.carvalho@suse.com>

> 
> Thanks,
> Shuhao
>>
>>>
>>> On Tue, Nov 4, 2025 at 9:21 AM Shuhao Fu <sfual@cse.ust.hk> wrote:
>>>>
>>>> Fix refcount leak in `smb2_set_path_attr` when path conversion fails.
>>>>
>>>> Function `cifs_get_writable_path` returns `cfile` with its reference
>>>> counter `cfile->count` increased on success. Function `smb2_compound_op`
>>>> would decrease the reference counter for `cfile`, as stated in its
>>>> comment. By calling `smb2_rename_path`, the reference counter of `cfile`
>>>> would leak if `cifs_convert_path_to_utf16` fails in `smb2_set_path_attr`.
>>>>
>>>> Fixes: 8de9e86c67ba ("cifs: create a helper to find a writeable handle by path name")
>>>> Signed-off-by: Shuhao Fu <sfual@cse.ust.hk>
>>>> ---
>>>>  fs/smb/client/smb2inode.c | 2 ++
>>>>  1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
>>>> index 09e3fc81d..69cb81fa0 100644
>>>> --- a/fs/smb/client/smb2inode.c
>>>> +++ b/fs/smb/client/smb2inode.c
>>>> @@ -1294,6 +1294,8 @@ static int smb2_set_path_attr(const unsigned int xid, struct cifs_tcon *tcon,
>>>>         smb2_to_name = cifs_convert_path_to_utf16(to_name, cifs_sb);
>>>>         if (smb2_to_name == NULL) {
>>>>                 rc = -ENOMEM;
>>>> +               if (cfile)
>>>> +                       cifsFileInfo_put(cfile);
>>>>                 goto smb2_rename_path;
>>>>         }
>>>>         in_iov.iov_base = smb2_to_name;
>>>> --
>>>> 2.39.5 (Apple Git-154)
>>>>
>>>>
>>>
>>>
>>
>> -- 
>> Henrique
>> SUSE Labs

-- 
Henrique
SUSE Labs