[PATCH 5.13 274/300] cifs: Do not leak EDEADLK to dgetents64 for STATUS_USER_SESSION_DELETED

Greg Kroah-Hartman
2021-09-13T14:20:16Z

From: Ronnie Sahlberg <lsahlber@redhat.com>

commit 3998f0b8bc49ec784990971dc1f16bf367b19078 upstream.

RHBZ: 1994393

If we hit a STATUS_USER_SESSION_DELETED for the Create part in the
Create/QueryDirectory compound that starts a directory scan
we will leak EDEADLK back to userspace and surprise glibc and the application.

Pick this up initiate_cifs_search() and retry a small number of tries before we
return an error to userspace.

Cc: stable@vger.kernel.org
Reported-by: Xiaoli Feng <xifeng@redhat.com>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/readdir.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -381,7 +381,7 @@ int get_symlink_reparse_path(char *full_
*/

static int
-initiate_cifs_search(const unsigned int xid, struct file *file,
+_initiate_cifs_search(const unsigned int xid, struct file *file,
const char *full_path)
{
__u16 search_flags;
@@ -463,6 +463,27 @@ error_exit:
return rc;
}

+static int
+initiate_cifs_search(const unsigned int xid, struct file *file,
+ const char *full_path)
+{
+ int rc, retry_count = 0;
+
+ do {
+ rc = _initiate_cifs_search(xid, file, full_path);
+ /*
+ * If we don't have enough credits to start reading the
+ * directory just try again after short wait.
+ */
+ if (rc != -EDEADLK)
+ break;
+
+ usleep_range(512, 2048);
+ } while (retry_count++ < 5);
+
+ return rc;
+}
+
/* return length of unicode string in bytes */
static int cifs_unicode_bytelen(const char *str)
{