Re: [f2fs-dev] [PATCH] f2fs: avoid null pointer access when handling IPU error

From: Chao Yu
Date: Tue May 11 2021 - 02:03:20 EST


On 2021/5/11 13:07, Jaegeuk Kim wrote:
On 05/11, Chao Yu wrote:
On 2021/5/10 22:28, Jaegeuk Kim wrote:
Unable to handle kernel NULL pointer dereference at virtual address 000000000000001a
pc : f2fs_inplace_write_data+0x144/0x208
lr : f2fs_inplace_write_data+0x134/0x208
Call trace:
f2fs_inplace_write_data+0x144/0x208
f2fs_do_write_data_page+0x270/0x770
f2fs_write_single_data_page+0x47c/0x830
__f2fs_write_data_pages+0x444/0x98c
f2fs_write_data_pages.llvm.16514453770497736882+0x2c/0x38
do_writepages+0x58/0x118
__writeback_single_inode+0x44/0x300
writeback_sb_inodes+0x4b8/0x9c8
wb_writeback+0x148/0x42c
wb_do_writeback+0xc8/0x390
wb_workfn+0xb0/0x2f4
process_one_work+0x1fc/0x444
worker_thread+0x268/0x4b4
kthread+0x13c/0x158
ret_from_fork+0x10/0x18

Fixes: 955772787667 ("f2fs: drop inplace IO if fs status is abnormal")

My bad, thanks for fixing this.

Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
fs/f2fs/segment.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index c605415840b5..ae875557d693 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -3577,9 +3577,11 @@ int f2fs_inplace_write_data(struct f2fs_io_info *fio)
if (fio->bio) {
struct bio *bio = *(fio->bio);
- bio->bi_status = BLK_STS_IOERR;
- bio_endio(bio);
- fio->bio = NULL;
+ if (bio) {
+ bio->bi_status = BLK_STS_IOERR;
+ bio_endio(bio);
+ fio->bio = NULL;

fio->bio points a bio assigned in writepages(), so it should reset
that bio to NULL by *(fio->bio) = NULL.

Good timing. I hit other kernel panic, and it seems this is the root cause.
Let me give it a try. :)

--- v2 ---

Unable to handle kernel NULL pointer dereference at virtual address 000000000000001a
pc : f2fs_inplace_write_data+0x144/0x208
lr : f2fs_inplace_write_data+0x134/0x208
Call trace:
f2fs_inplace_write_data+0x144/0x208
f2fs_do_write_data_page+0x270/0x770
f2fs_write_single_data_page+0x47c/0x830
__f2fs_write_data_pages+0x444/0x98c
f2fs_write_data_pages.llvm.16514453770497736882+0x2c/0x38
do_writepages+0x58/0x118
__writeback_single_inode+0x44/0x300
writeback_sb_inodes+0x4b8/0x9c8
wb_writeback+0x148/0x42c
wb_do_writeback+0xc8/0x390
wb_workfn+0xb0/0x2f4
process_one_work+0x1fc/0x444
worker_thread+0x268/0x4b4
kthread+0x13c/0x158
ret_from_fork+0x10/0x18

Fixes: 955772787667 ("f2fs: drop inplace IO if fs status is abnormal")
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>

Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>

Thanks,