[PATCH 5.10 26/77] ocfs2: fix race between searching chunks and release journal_head from buffer_head

Greg Kroah-Hartman
2021-11-01T09:34:41Z

From: Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>

commit 6f1b228529ae49b0f85ab89bcdb6c365df401558 upstream.

Encountered a race between ocfs2_test_bg_bit_allocatable() and
jbd2_journal_put_journal_head() resulting in the below vmcore.

PID: 106879 TASK: ffff880244ba9c00 CPU: 2 COMMAND: "loop3"
Call trace:
panic
oops_end
no_context
__bad_area_nosemaphore
bad_area_nosemaphore
__do_page_fault
do_page_fault
page_fault
[exception RIP: ocfs2_block_group_find_clear_bits+316]
ocfs2_block_group_find_clear_bits [ocfs2]
ocfs2_cluster_group_search [ocfs2]
ocfs2_search_chain [ocfs2]
ocfs2_claim_suballoc_bits [ocfs2]
__ocfs2_claim_clusters [ocfs2]
ocfs2_claim_clusters [ocfs2]
ocfs2_local_alloc_slide_window [ocfs2]
ocfs2_reserve_local_alloc_bits [ocfs2]
ocfs2_reserve_clusters_with_limit [ocfs2]
ocfs2_reserve_clusters [ocfs2]
ocfs2_lock_refcount_allocators [ocfs2]
ocfs2_make_clusters_writable [ocfs2]
ocfs2_replace_cow [ocfs2]
ocfs2_refcount_cow [ocfs2]
ocfs2_file_write_iter [ocfs2]
lo_rw_aio
loop_queue_work
kthread_worker_fn
kthread
ret_from_fork

When ocfs2_test_bg_bit_allocatable() called bh2jh(bg_bh), the
bg_bh->b_private NULL as jbd2_journal_put_journal_head() raced and
released the jounal head from the buffer head. Needed to take bit lock
for the bit 'BH_JournalHead' to fix this race.

Link: https://lkml.kernel.org/r/1634820718-6043-1-git-send-email-gautham.ananthakrishna@oracle.com
Signed-off-by: Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: <rajesh.sivaramasubramaniom@oracle.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ocfs2/suballoc.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)

--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -1253,7 +1253,7 @@ static int ocfs2_test_bg_bit_allocatable
{
struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) bg_bh->b_data;
struct journal_head *jh;
- int ret;
+ int ret = 1;

if (ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap))
return 0;
@@ -1261,14 +1261,18 @@ static int ocfs2_test_bg_bit_allocatable
if (!buffer_jbd(bg_bh))
return 1;

- jh = bh2jh(bg_bh);
- spin_lock(&jh->b_state_lock);
- bg = (struct ocfs2_group_desc *) jh->b_committed_data;
- if (bg)
- ret = !ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap);
- else
- ret = 1;
- spin_unlock(&jh->b_state_lock);
+ jbd_lock_bh_journal_head(bg_bh);
+ if (buffer_jbd(bg_bh)) {
+ jh = bh2jh(bg_bh);
+ spin_lock(&jh->b_state_lock);
+ bg = (struct ocfs2_group_desc *) jh->b_committed_data;
+ if (bg)
+ ret = !ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap);
+ else
+ ret = 1;
+ spin_unlock(&jh->b_state_lock);
+ }
+ jbd_unlock_bh_journal_head(bg_bh);

return ret;
}