linux-kernel - [PATCH 4.4 27/41] btrfs: fix NULL pointer dereference from free_reloc

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Message-Id: <20171003114221.587736093@linuxfoundation.org>
Date:   Tue,  3 Oct 2017 14:21:28 +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, Naohiro Aota <naohiro.aota@....com>,
        Nikolay Borisov <nborisov@...e.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 4.4 27/41] btrfs: fix NULL pointer dereference from free_reloc_roots()

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

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

From: Naohiro Aota <naohiro.aota@....com>

commit bb166d7207432d3c7d10c45dc052f12ba3a2121d upstream.

__del_reloc_root should be called before freeing up reloc_root->node.
If not, calling __del_reloc_root() dereference reloc_root->node, causing
the system BUG.

Fixes: 6bdf131fac23 ("Btrfs: don't leak reloc root nodes on error")
Signed-off-by: Naohiro Aota <naohiro.aota@....com>
Reviewed-by: Nikolay Borisov <nborisov@...e.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/relocation.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2350,11 +2350,11 @@ void free_reloc_roots(struct list_head *
 	while (!list_empty(list)) {
 		reloc_root = list_entry(list->next, struct btrfs_root,
 					root_list);
+		__del_reloc_root(reloc_root);
 		free_extent_buffer(reloc_root->node);
 		free_extent_buffer(reloc_root->commit_root);
 		reloc_root->node = NULL;
 		reloc_root->commit_root = NULL;
-		__del_reloc_root(reloc_root);
 	}
 }