From: Aurelien Aptel aaptel@suse.com
commit 7e5a70ad88b1e6f6d9b934b2efb41afff496820f upstream.
Prevent deadlock between open_shroot() and cifs_mark_open_files_invalid() by releasing the lock before entering SMB2_open, taking it again after and checking if we still need to use the result.
Link: https://lore.kernel.org/linux-cifs/684ed01c-cbca-2716-bc28-b0a59a0f8521@prod... Fixes: 3d4ef9a15343 ("smb3: fix redundant opens on root") Signed-off-by: Aurelien Aptel aaptel@suse.com Reviewed-by: Pavel Shilovsky pshilov@microsoft.com Signed-off-by: Steve French stfrench@microsoft.com CC: Stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/cifs/smb2ops.c | 46 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 45 insertions(+), 1 deletion(-)
--- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -705,8 +705,51 @@ int open_shroot(unsigned int xid, struct
smb2_set_related(&rqst[1]);
+ /* + * We do not hold the lock for the open because in case + * SMB2_open needs to reconnect, it will end up calling + * cifs_mark_open_files_invalid() which takes the lock again + * thus causing a deadlock + */ + + mutex_unlock(&tcon->crfid.fid_mutex); rc = compound_send_recv(xid, ses, flags, 2, rqst, resp_buftype, rsp_iov); + mutex_lock(&tcon->crfid.fid_mutex); + + /* + * Now we need to check again as the cached root might have + * been successfully re-opened from a concurrent process + */ + + if (tcon->crfid.is_valid) { + /* work was already done */ + + /* stash fids for close() later */ + struct cifs_fid fid = { + .persistent_fid = pfid->persistent_fid, + .volatile_fid = pfid->volatile_fid, + }; + + /* + * caller expects this func to set pfid to a valid + * cached root, so we copy the existing one and get a + * reference. + */ + memcpy(pfid, tcon->crfid.fid, sizeof(*pfid)); + kref_get(&tcon->crfid.refcount); + + mutex_unlock(&tcon->crfid.fid_mutex); + + if (rc == 0) { + /* close extra handle outside of crit sec */ + SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid); + } + goto oshr_free; + } + + /* Cached root is still invalid, continue normaly */ + if (rc) goto oshr_exit;
@@ -740,8 +783,9 @@ int open_shroot(unsigned int xid, struct (char *)&tcon->crfid.file_all_info)) tcon->crfid.file_all_info_is_valid = 1;
- oshr_exit: +oshr_exit: mutex_unlock(&tcon->crfid.fid_mutex); +oshr_free: SMB2_open_free(&rqst[0]); SMB2_query_info_free(&rqst[1]); free_rsp_buf(resp_buftype[0], rsp_iov[0].iov_base);