open_shroot() invokes kref_get(), which increases the refcount of the
"tcon->crfid" object. When open_shroot() returns not zero, it means the
open operation failed and close_shroot() will not be called to decrement
the refcount of the "tcon->crfid".
The reference counting issue happens in one normal path of
open_shroot(). When the cached root have been opened successfully in a
concurrent process, the function increases the refcount and jump to
"oshr_free" to return. However the current return value "rc" may not
equal to 0, thus the increased refcount will not be balanced outside the
function, causing a refcnt leak.
Fix this issue by setting the value of "rc" to 0 before jumping to
"oshr_free" label.
Signed-off-by: Xiyu Yang <[email protected]>
Signed-off-by: Xin Tan <[email protected]>
---
fs/cifs/smb2ops.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 736d86b8a910..28553d45604e 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -763,6 +763,7 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon,
/* close extra handle outside of crit sec */
SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
}
+ rc = 0;
goto oshr_free;
}
--
2.7.4
added cc:stable and merged into cifs-2.6.git for-next
On Sat, Jun 13, 2020 at 7:36 AM Xiyu Yang <[email protected]> wrote:
>
> open_shroot() invokes kref_get(), which increases the refcount of the
> "tcon->crfid" object. When open_shroot() returns not zero, it means the
> open operation failed and close_shroot() will not be called to decrement
> the refcount of the "tcon->crfid".
>
> The reference counting issue happens in one normal path of
> open_shroot(). When the cached root have been opened successfully in a
> concurrent process, the function increases the refcount and jump to
> "oshr_free" to return. However the current return value "rc" may not
> equal to 0, thus the increased refcount will not be balanced outside the
> function, causing a refcnt leak.
>
> Fix this issue by setting the value of "rc" to 0 before jumping to
> "oshr_free" label.
>
> Signed-off-by: Xiyu Yang <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>
> ---
> fs/cifs/smb2ops.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index 736d86b8a910..28553d45604e 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -763,6 +763,7 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon,
> /* close extra handle outside of crit sec */
> SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
> }
> + rc = 0;
> goto oshr_free;
> }
>
> --
> 2.7.4
>
--
Thanks,
Steve