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KMSAN: uninit-value in longest_match

Status: fixed on 2023/06/08 14:41
Subsystems: btrfs
[Documentation on labels]
Reported-by: syzbot+14d9e7602ebdf7ec0a60@syzkaller.appspotmail.com
Fix commit: eadd7deca0ad btrfs: zlib: zero-initialize zlib workspace
First crash: 781d, last: 776d
▶ ▼ Discussions (5)
Title Replies (including bot) Last reply
[PATCH AUTOSEL 6.1 01/93] hv_netvsc: Allocate memory in netvsc_dma_map() with GFP_ATOMIC 3 (3) 2023/02/15 07:04
[PATCH] btrfs: zlib: zero-initialize zlib workspace 2 (2) 2023/01/24 16:59
Re: [syzbot] KMSAN: uninit-value in longest_match 2 (2) 2023/01/24 11:07
Re: [syzbot] KMSAN: uninit-value in longest_match 1 (1) 2022/12/14 14:16
[syzbot] KMSAN: uninit-value in longest_match 1 (2) 2022/12/13 06:40

Sample crash report:
=====================================================
BUG: KMSAN: uninit-value in longest_match+0xc88/0x1220 lib/zlib_deflate/deflate.c:668
 longest_match+0xc88/0x1220 lib/zlib_deflate/deflate.c:668
 deflate_fast+0x1838/0x2280 lib/zlib_deflate/deflate.c:954
 zlib_deflate+0x1783/0x22b0 lib/zlib_deflate/deflate.c:410
 zlib_compress_pages+0xd34/0x1f90 fs/btrfs/zlib.c:178
 compression_compress_pages fs/btrfs/compression.c:77 [inline]
 btrfs_compress_pages+0x325/0x440 fs/btrfs/compression.c:1208
 compress_file_range+0x11ac/0x3510 fs/btrfs/inode.c:730
 async_cow_start+0x33/0xd0 fs/btrfs/inode.c:1458
 btrfs_work_helper+0x55a/0x990 fs/btrfs/async-thread.c:280
 process_one_work+0xb27/0x13e0 kernel/workqueue.c:2289
 worker_thread+0x1076/0x1d60 kernel/workqueue.c:2436
 kthread+0x31b/0x430 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

Uninit was created at:
 __kmalloc_large_node+0x2f7/0x3a0 mm/slab_common.c:1106
 __do_kmalloc_node mm/slab_common.c:943 [inline]
 __kmalloc_node+0x1d2/0x3c0 mm/slab_common.c:962
 kmalloc_node include/linux/slab.h:579 [inline]
 kvmalloc_node+0xbc/0x2d0 mm/util.c:581
 kvmalloc include/linux/slab.h:706 [inline]
 zlib_alloc_workspace+0x111/0x5e0 fs/btrfs/zlib.c:66
 alloc_workspace+0x329/0x5a0 fs/btrfs/compression.c:939
 btrfs_init_workspace_manager+0x11f/0x4d0 fs/btrfs/compression.c:982
 btrfs_init_compress+0x1f/0x30 fs/btrfs/compression.c:1249
 init_btrfs_fs+0x94/0x5f2 fs/btrfs/super.c:2736
 do_one_initcall+0x221/0x860 init/main.c:1303
 do_initcall_level+0x146/0x322 init/main.c:1376
 do_initcalls+0x11a/0x201 init/main.c:1392
 do_basic_setup+0x22/0x24 init/main.c:1411
 kernel_init_freeable+0x308/0x4d0 init/main.c:1631
 kernel_init+0x2b/0x7d0 init/main.c:1519
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

CPU: 0 PID: 39 Comm: kworker/u4:2 Not tainted 6.1.0-syzkaller-64311-g5c6259d6d19f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Workqueue: btrfs-delalloc btrfs_work_helper
=====================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2022/12/14 05:40 https://github.com/google/kmsan.git master 5c6259d6d19f e660de91 .config console log report info ci-upstream-kmsan-gce-386 KMSAN: uninit-value in longest_match
2022/12/09 20:07 https://github.com/google/kmsan.git master 30d2727189c5 67be1ae7 .config console log report info ci-upstream-kmsan-gce-386 KMSAN: uninit-value in longest_match
2022/12/09 06:54 https://github.com/google/kmsan.git master 30d2727189c5 1034e5fa .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386 KMSAN: uninit-value in longest_match
2022/12/09 08:13 https://github.com/google/kmsan.git master 30d2727189c5 1034e5fa .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386 KMSAN: uninit-value in zlib_tr_flush_block
* Struck through repros no longer work on HEAD.