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authorAurelien Aptel <aaptel@suse.com>2019-07-17 12:46:28 +0200
committerSteve French <stfrench@microsoft.com>2019-07-18 13:51:35 -0500
commit7e5a70ad88b1e6f6d9b934b2efb41afff496820f (patch)
tree9c13366cebf1ad4eccc41e40ca9005e55305d2f5 /fs/cifs
parentae9b728c8dc0a9939d89f84e8603258ca2a0df22 (diff)
CIFS: fix deadlock in cached root handling
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@prodrive-technologies.com/T/#u 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>
Diffstat (limited to 'fs/cifs')
-rw-r--r--fs/cifs/smb2ops.c46
1 files changed, 45 insertions, 1 deletions
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 0cdc4e47ca87..fed75e1646c1 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -694,8 +694,51 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
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;
@@ -729,8 +772,9 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
(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);