[PATCH 3.16.y-ckt 029/126] ext4: fix potential use after free in __ext4_journal_stop

From: Luis Henriques
Date: Wed Dec 09 2015 - 05:35:14 EST

3.16.7-ckt21 -stable review patch. If anyone has any objections, please let me know.


From: Lukas Czerner <lczerner@xxxxxxxxxx>

commit 6934da9238da947628be83635e365df41064b09b upstream.

There is a use-after-free possibility in __ext4_journal_stop() in the
case that we free the handle in the first jbd2_journal_stop() because
we're referencing handle->h_err afterwards. This was introduced in
9705acd63b125dee8b15c705216d7186daea4625 and it is wrong. Fix it by
storing the handle->h_err value beforehand and avoid referencing
potentially freed handle.

Fixes: 9705acd63b125dee8b15c705216d7186daea4625
Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
fs/ext4/ext4_jbd2.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index 44c89188c62c..23349f00e77c 100644
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -88,13 +88,13 @@ int __ext4_journal_stop(const char *where, unsigned int line, handle_t *handle)
return 0;

+ err = handle->h_err;
if (!handle->h_transaction) {
- err = jbd2_journal_stop(handle);
- return handle->h_err ? handle->h_err : err;
+ rc = jbd2_journal_stop(handle);
+ return err ? err : rc;

sb = handle->h_transaction->t_journal->j_private;
- err = handle->h_err;
rc = jbd2_journal_stop(handle);

if (!err)
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