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authorDaeho Jeong <daehojeong@google.com>2020-12-05 13:26:26 +0900
committerJaegeuk Kim <jaegeuk@kernel.org>2020-12-08 15:39:14 -0800
commit6422a71ef40e4751d59b8c9412e7e2dafe085878 (patch)
treef348f6fcb940c7dabef51994d049cb7f7ce090de /fs/f2fs/f2fs.h
parent96dd02519580faa731066351f438a2f967d9a0ee (diff)
downloadlinux-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/f2fs.h')
-rw-r--r--fs/f2fs/f2fs.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 594df6391390..7364d453783f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1354,6 +1354,7 @@ struct decompress_io_ctx {
size_t rlen; /* valid data length in rbuf */
size_t clen; /* valid data length in cbuf */
atomic_t pending_pages; /* in-flight compressed page count */
+ atomic_t verity_pages; /* in-flight page count for verity */
bool failed; /* indicate IO error during decompression */
void *private; /* payload buffer for specified decompression algorithm */
void *private2; /* extra payload buffer */