linux-kernel - [PATCH 3.4 29/43] reiserfs: fix race in readdir

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Date:	Sun,  4 May 2014 11:42:23 -0400
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Jeff Mahoney <jeffm@...e.com>,
	Jan Kara <jack@...e.cz>
Subject: [PATCH 3.4 29/43] reiserfs: fix race in readdir

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jeff Mahoney <jeffm@...e.com>

commit 01d8885785a60ae8f4c37b0ed75bdc96d0fc6a44 upstream.

jdm-20004 reiserfs_delete_xattrs: Couldn't delete all xattrs (-2)

The -ENOENT is due to readdir calling dir_emit on the same entry twice.

If the dir_emit callback sleeps and the tree is changed underneath us,
we won't be able to trust deh_offset(deh) anymore. We need to save
next_pos before we might sleep so we can find the next entry.

Signed-off-by: Jeff Mahoney <jeffm@...e.com>
Signed-off-by: Jan Kara <jack@...e.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/reiserfs/dir.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/reiserfs/dir.c
+++ b/fs/reiserfs/dir.c
@@ -128,6 +128,7 @@ int reiserfs_readdir_dentry(struct dentr
 				char *d_name;
 				off_t d_off;
 				ino_t d_ino;
+				loff_t cur_pos = deh_offset(deh);
 
 				if (!de_visible(deh))
 					/* it is hidden entry */
@@ -200,8 +201,9 @@ int reiserfs_readdir_dentry(struct dentr
 				if (local_buf != small_buf) {
 					kfree(local_buf);
 				}
-				// next entry should be looked for with such offset
-				next_pos = deh_offset(deh) + 1;
+
+				/* deh_offset(deh) may be invalid now. */
+				next_pos = cur_pos + 1;
 
 				if (item_moved(&tmp_ih, &path_to_entry)) {
 					goto research;


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