linux-kernel - [PATCH 4.9 130/153] f2fs: fix a problem of using memory after free

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Message-Id: <20170310083954.915179947@linuxfoundation.org>
Date:   Fri, 10 Mar 2017 10:09:23 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yunlei He <heyunlei@...wei.com>,
        Chao Yu <yuchao0@...wei.com>, Jaegeuk Kim <jaegeuk@...nel.org>
Subject: [PATCH 4.9 130/153] f2fs: fix a problem of using memory after free

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

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

From: Yunlei He <heyunlei@...wei.com>

commit 7855eba4d6102f811b6dd142d6c749f53b591fa3 upstream.

This patch fix a problem of using memory after free
in function __try_merge_extent_node.

Fixes: 0f825ee6e873 ("f2fs: add new interfaces for extent tree")
Signed-off-by: Yunlei He <heyunlei@...wei.com>
Reviewed-by: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/f2fs/extent_cache.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -352,11 +352,12 @@ static struct extent_node *__try_merge_e
 	}
 
 	if (next_ex && __is_front_mergeable(ei, &next_ex->ei)) {
-		if (en)
-			__release_extent_node(sbi, et, prev_ex);
 		next_ex->ei.fofs = ei->fofs;
 		next_ex->ei.blk = ei->blk;
 		next_ex->ei.len += ei->len;
+		if (en)
+			__release_extent_node(sbi, et, prev_ex);
+
 		en = next_ex;
 	}