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| author | Jan Kara <jack@suse.cz> | 2018-10-06 01:44:40 +0300 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2018-10-06 01:44:40 +0300 |
| commit | ccd3c4373eacb044eb3832966299d13d2631f66f (patch) | |
| tree | ef20ba8dba7c3d9346f31a2a559366beb71eac29 /fs/jbd2 | |
| parent | 182a79e0c17147d2c2d3990a9a7b6b58a1561c7a (diff) | |
| download | linux-ccd3c4373eacb044eb3832966299d13d2631f66f.tar.xz | |
jbd2: fix use after free in jbd2_log_do_checkpoint()
The code cleaning transaction's lists of checkpoint buffers has a bug
where it increases bh refcount only after releasing
journal->j_list_lock. Thus the following race is possible:
CPU0 CPU1
jbd2_log_do_checkpoint()
jbd2_journal_try_to_free_buffers()
__journal_try_to_free_buffer(bh)
...
while (transaction->t_checkpoint_io_list)
...
if (buffer_locked(bh)) {
<-- IO completes now, buffer gets unlocked -->
spin_unlock(&journal->j_list_lock);
spin_lock(&journal->j_list_lock);
__jbd2_journal_remove_checkpoint(jh);
spin_unlock(&journal->j_list_lock);
try_to_free_buffers(page);
get_bh(bh) <-- accesses freed bh
Fix the problem by grabbing bh reference before unlocking
journal->j_list_lock.
Fixes: dc6e8d669cf5 ("jbd2: don't call get_bh() before calling __jbd2_journal_remove_checkpoint()")
Fixes: be1158cc615f ("jbd2: fold __process_buffer() into jbd2_log_do_checkpoint()")
Reported-by: syzbot+7f4a27091759e2fe7453@syzkaller.appspotmail.com
CC: stable@vger.kernel.org
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/jbd2')
| -rw-r--r-- | fs/jbd2/checkpoint.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c index c125d662777c..26f8d7e46462 100644 --- a/fs/jbd2/checkpoint.c +++ b/fs/jbd2/checkpoint.c @@ -251,8 +251,8 @@ restart: bh = jh2bh(jh); if (buffer_locked(bh)) { - spin_unlock(&journal->j_list_lock); get_bh(bh); + spin_unlock(&journal->j_list_lock); wait_on_buffer(bh); /* the journal_head may have gone by now */ BUFFER_TRACE(bh, "brelse"); @@ -333,8 +333,8 @@ restart2: jh = transaction->t_checkpoint_io_list; bh = jh2bh(jh); if (buffer_locked(bh)) { - spin_unlock(&journal->j_list_lock); get_bh(bh); + spin_unlock(&journal->j_list_lock); wait_on_buffer(bh); /* the journal_head may have gone by now */ BUFFER_TRACE(bh, "brelse"); |