linux-kernel - [PATCH 3.11 116/182] reiserfs: fix race in readdir

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Message-Id: <1398329507-5911-117-git-send-email-luis.henriques@canonical.com>
Date:	Thu, 24 Apr 2014 09:50:41 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jeff Mahoney <jeffm@...e.com>, Jan Kara <jack@...e.cz>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.11 116/182] reiserfs: fix race in readdir

3.11.10.9 -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: Luis Henriques <luis.henriques@...onical.com>
---
 fs/reiserfs/dir.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/reiserfs/dir.c b/fs/reiserfs/dir.c
index 03e4ca5..79b7b55 100644
--- a/fs/reiserfs/dir.c
+++ b/fs/reiserfs/dir.c
@@ -124,6 +124,7 @@ int reiserfs_readdir_inode(struct inode *inode, struct dir_context *ctx)
 				int d_reclen;
 				char *d_name;
 				ino_t d_ino;
+				loff_t cur_pos = deh_offset(deh);
 
 				if (!de_visible(deh))
 					/* it is hidden entry */
@@ -195,8 +196,9 @@ int reiserfs_readdir_inode(struct inode *inode, struct dir_context *ctx)
 				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)) {
 					set_cpu_key_k_offset(&pos_key,
-- 
1.9.1

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