[PATCH] f2fs: fix NULL pointer dereference in f2fs_submit_page_write()

[Wenjie]

From: Wenjie Qi <qwjhust@xxxxxxxxx>

BUG: kernel NULL pointer dereference, address: 0000000000000014
RIP: 0010:f2fs_submit_page_write+0x6cf/0x780 [f2fs]
Call Trace:
<TASK>
? show_regs+0x6e/0x80
? __die+0x29/0x70
? page_fault_oops+0x154/0x4a0
? prb_read_valid+0x20/0x30
? __irq_work_queue_local+0x39/0xd0
? irq_work_queue+0x36/0x70
? do_user_addr_fault+0x314/0x6c0
? exc_page_fault+0x7d/0x190
? asm_exc_page_fault+0x2b/0x30
? f2fs_submit_page_write+0x6cf/0x780 [f2fs]
? f2fs_submit_page_write+0x736/0x780 [f2fs]
do_write_page+0x50/0x170 [f2fs]
f2fs_outplace_write_data+0x61/0xb0 [f2fs]
f2fs_do_write_data_page+0x3f8/0x660 [f2fs]
f2fs_write_single_data_page+0x5bb/0x7a0 [f2fs]
f2fs_write_cache_pages+0x3da/0xbe0 [f2fs]
...

It is possible that other threads have added this fio to io->bio
and submitted the io->bio before entering f2fs_submit_page_write().
At this point io->bio = NULL.
If is_end_zone_blkaddr(sbi, fio->new_blkaddr) of this fio is true,
then an NULL pointer dereference error occurs at bio_get(io->bio).
In this case, the code to determine the zone end can simply be skipped.

Signed-off-by: Wenjie Qi <qwjhust@xxxxxxxxx>
---
 fs/f2fs/data.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 1896928cae77..d08e92bb2621 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1100,7 +1100,7 @@ void f2fs_submit_page_write(struct f2fs_io_info *fio)
 		goto next;
 out:
 #ifdef CONFIG_BLK_DEV_ZONED
-	if (f2fs_sb_has_blkzoned(sbi) && btype < META &&
+	if (io->bio && f2fs_sb_has_blkzoned(sbi) && btype < META &&
 			is_end_zone_blkaddr(sbi, fio->new_blkaddr)) {
 		spin_lock_bh(&sbi->available_active_zones_lock);
 		if (sbi->available_active_zones > 0) {
-- 
2.34.1