jbd2: fix potential use-after-free in jbd2_fc_wait_bufs

commit 243d1a5d505d0b0460c9af0ad56ed4a56ef0bebd upstream.

In 'jbd2_fc_wait_bufs' use 'bh' after put buffer head reference count
which may lead to use-after-free.
So judge buffer if uptodate before put buffer head reference count.

Cc: stable@kernel.org
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220914100812.1414768-3-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index a6efcf5..097ba72 100644 (file)
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -924,16 +924,16 @@ int jbd2_fc_wait_bufs(journal_t *journal, int num_blks)
        for (i = j_fc_off - 1; i >= j_fc_off - num_blks; i--) {
                bh = journal->j_fc_wbuf[i];
                wait_on_buffer(bh);
-               put_bh(bh);
-               journal->j_fc_wbuf[i] = NULL;
                /*
                 * Update j_fc_off so jbd2_fc_release_bufs can release remain
                 * buffer head.
                 */
                if (unlikely(!buffer_uptodate(bh))) {
-                       journal->j_fc_off = i;
+                       journal->j_fc_off = i + 1;
                        return -EIO;
                }
+               put_bh(bh);
+               journal->j_fc_wbuf[i] = NULL;
        }
 
        return 0;