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| author | Daeho Jeong <daehojeong@google.com> | 2020-12-05 13:26:26 +0900 |
|---|---|---|
| committer | Jaegeuk Kim <jaegeuk@kernel.org> | 2020-12-08 15:39:14 -0800 |
| commit | 6422a71ef40e4751d59b8c9412e7e2dafe085878 (patch) | |
| tree | f348f6fcb940c7dabef51994d049cb7f7ce090de /fs/f2fs/compress.c | |
| parent | 96dd02519580faa731066351f438a2f967d9a0ee (diff) | |
| download | linux-6422a71ef40e4751d59b8c9412e7e2dafe085878.tar.bz2 | |
f2fs: fix race of pending_pages in decompression
I found out f2fs_free_dic() is invoked in a wrong timing, but
f2fs_verify_bio() still needed the dic info and it triggered the
below kernel panic. It has been caused by the race condition of
pending_pages value between decompression and verity logic, when
the same compression cluster had been split in different bios.
By split bios, f2fs_verify_bio() ended up with decreasing
pending_pages value before it is reset to nr_cpages by
f2fs_decompress_pages() and caused the kernel panic.
[ 4416.564763] Unable to handle kernel NULL pointer dereference
at virtual address 0000000000000000
...
[ 4416.896016] Workqueue: fsverity_read_queue f2fs_verity_work
[ 4416.908515] pc : fsverity_verify_page+0x20/0x78
[ 4416.913721] lr : f2fs_verify_bio+0x11c/0x29c
[ 4416.913722] sp : ffffffc019533cd0
[ 4416.913723] x29: ffffffc019533cd0 x28: 0000000000000402
[ 4416.913724] x27: 0000000000000001 x26: 0000000000000100
[ 4416.913726] x25: 0000000000000001 x24: 0000000000000004
[ 4416.913727] x23: 0000000000001000 x22: 0000000000000000
[ 4416.913728] x21: 0000000000000000 x20: ffffffff2076f9c0
[ 4416.913729] x19: ffffffff2076f9c0 x18: ffffff8a32380c30
[ 4416.913731] x17: ffffffc01f966d97 x16: 0000000000000298
[ 4416.913732] x15: 0000000000000000 x14: 0000000000000000
[ 4416.913733] x13: f074faec89ffffff x12: 0000000000000000
[ 4416.913734] x11: 0000000000001000 x10: 0000000000001000
[ 4416.929176] x9 : ffffffff20d1f5c7 x8 : 0000000000000000
[ 4416.929178] x7 : 626d7464ff286b6b x6 : ffffffc019533ade
[ 4416.929179] x5 : 000000008049000e x4 : ffffffff2793e9e0
[ 4416.929180] x3 : 000000008049000e x2 : ffffff89ecfa74d0
[ 4416.929181] x1 : 0000000000000c40 x0 : ffffffff2076f9c0
[ 4416.929184] Call trace:
[ 4416.929187] fsverity_verify_page+0x20/0x78
[ 4416.929189] f2fs_verify_bio+0x11c/0x29c
[ 4416.929192] f2fs_verity_work+0x58/0x84
[ 4417.050667] process_one_work+0x270/0x47c
[ 4417.055354] worker_thread+0x27c/0x4d8
[ 4417.059784] kthread+0x13c/0x320
[ 4417.063693] ret_from_fork+0x10/0x18
Chao pointed this can happen by the below race condition.
Thread A f2fs_post_read_wq fsverity_wq
- f2fs_read_multi_pages()
- f2fs_alloc_dic
- dic->pending_pages = 2
- submit_bio()
- submit_bio()
- f2fs_post_read_work() handle first bio
- f2fs_decompress_work()
- __read_end_io()
- f2fs_decompress_pages()
- dic->pending_pages--
- enqueue f2fs_verity_work()
- f2fs_verity_work() handle first bio
- f2fs_verify_bio()
- dic->pending_pages--
- f2fs_post_read_work() handle second bio
- f2fs_decompress_work()
- enqueue f2fs_verity_work()
- f2fs_verify_pages()
- f2fs_free_dic()
- f2fs_verity_work() handle second bio
- f2fs_verfy_bio()
- use-after-free on dic
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'fs/f2fs/compress.c')
| -rw-r--r-- | fs/f2fs/compress.c | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c index d23bebb6ccd3..f05d409fd0ed 100644 --- a/fs/f2fs/compress.c +++ b/fs/f2fs/compress.c @@ -821,8 +821,6 @@ destroy_decompress_ctx: if (cops->destroy_decompress_ctx) cops->destroy_decompress_ctx(dic); out_free_dic: - if (verity) - atomic_set(&dic->pending_pages, dic->nr_cpages); if (!verity) f2fs_decompress_end_io(dic->rpages, dic->cluster_size, ret, false); |