From: Rohith Surabattula <rohiths@microsoft.com>
Date: Thu, 29 Jul 2021 07:45:29 +0000 (+0000)
Subject: cifs: Handle race conditions during rename
X-Git-Tag: microblaze-v5.16~301^2~1
X-Git-Url: http://git.monstr.eu/?p=linux-2.6-microblaze.git;a=commitdiff_plain;h=41535701da3324b80029cabb501e86c4fafe339d

cifs: Handle race conditions during rename

When rename is executed on directory which has files for which
close is deferred, then rename will fail with EACCES.

This patch will try to close all deferred files when EACCES is received
and retry rename on a directory.

Signed-off-by: Rohith Surabattula <rohiths@microsoft.com>
Cc: stable@vger.kernel.org # 5.13
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index b96b253e7635..65f8a70cece3 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1625,7 +1625,7 @@ int cifs_unlink(struct inode *dir, struct dentry *dentry)
 		goto unlink_out;
 	}
 
-	cifs_close_all_deferred_files(tcon);
+	cifs_close_deferred_file(CIFS_I(inode));
 	if (cap_unix(tcon->ses) && (CIFS_UNIX_POSIX_PATH_OPS_CAP &
 				le64_to_cpu(tcon->fsUnixInfo.Capability))) {
 		rc = CIFSPOSIXDelFile(xid, tcon, full_path,
@@ -2084,6 +2084,7 @@ cifs_rename2(struct user_namespace *mnt_userns, struct inode *source_dir,
 	FILE_UNIX_BASIC_INFO *info_buf_target;
 	unsigned int xid;
 	int rc, tmprc;
+	int retry_count = 0;
 
 	if (flags & ~RENAME_NOREPLACE)
 		return -EINVAL;
@@ -2113,10 +2114,24 @@ cifs_rename2(struct user_namespace *mnt_userns, struct inode *source_dir,
 		goto cifs_rename_exit;
 	}
 
-	cifs_close_all_deferred_files(tcon);
+	cifs_close_deferred_file(CIFS_I(d_inode(source_dentry)));
+	if (d_inode(target_dentry) != NULL)
+		cifs_close_deferred_file(CIFS_I(d_inode(target_dentry)));
+
 	rc = cifs_do_rename(xid, source_dentry, from_name, target_dentry,
 			    to_name);
 
+	if (rc == -EACCES) {
+		while (retry_count < 3) {
+			cifs_close_all_deferred_files(tcon);
+			rc = cifs_do_rename(xid, source_dentry, from_name, target_dentry,
+					    to_name);
+			if (rc != -EACCES)
+				break;
+			retry_count++;
+		}
+	}
+
 	/*
 	 * No-replace is the natural behavior for CIFS, so skip unlink hacks.
 	 */
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 844abeb2b48f..cdb1ec1461de 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -723,13 +723,19 @@ void
 cifs_close_deferred_file(struct cifsInodeInfo *cifs_inode)
 {
 	struct cifsFileInfo *cfile = NULL;
-	struct cifs_deferred_close *dclose;
+
+	if (cifs_inode == NULL)
+		return;
 
 	list_for_each_entry(cfile, &cifs_inode->openFileList, flist) {
-		spin_lock(&cifs_inode->deferred_lock);
-		if (cifs_is_deferred_close(cfile, &dclose))
-			mod_delayed_work(deferredclose_wq, &cfile->deferred, 0);
-		spin_unlock(&cifs_inode->deferred_lock);
+		if (delayed_work_pending(&cfile->deferred)) {
+			/*
+			 * If there is no pending work, mod_delayed_work queues new work.
+			 * So, Increase the ref count to avoid use-after-free.
+			 */
+			if (!mod_delayed_work(deferredclose_wq, &cfile->deferred, 0))
+				cifsFileInfo_get(cfile);
+		}
 	}
 }