linux-kernel - [PATCH 5.14 306/334] cifs: Do not leak EDEADLK to dgetents64 for STATUS_USER_SESSION

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Message-Id: <20210913131123.762721637@linuxfoundation.org>
Date:   Mon, 13 Sep 2021 15:16:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xiaoli Feng <xifeng@...hat.com>,
        Ronnie Sahlberg <lsahlber@...hat.com>,
        Steve French <stfrench@...rosoft.com>
Subject: [PATCH 5.14 306/334] cifs: Do not leak EDEADLK to dgetents64 for STATUS_USER_SESSION_DELETED

From: Ronnie Sahlberg <lsahlber@...hat.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@...r.kernel.org
Reported-by: Xiaoli Feng <xifeng@...hat.com>
Signed-off-by: Ronnie Sahlberg <lsahlber@...hat.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/cifs/readdir.c |   23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -369,7 +369,7 @@ 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;
@@ -451,6 +451,27 @@ 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)
 {