[syzbot] KMSAN: uninit-value in longest_match

[syzbot <syzbot+14d9e7602ebdf7ec0a60@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    30d2727189c5 kmsan: fix memcpy tests
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=117d38f5880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a2144983ada8b4f3
dashboard link: https://syzkaller.appspot.com/bug?extid=14d9e7602ebdf7ec0a60
compiler:       clang version 15.0.0 (https://github.com/llvm/llvm-project.git 610139d2d9ce6746b3c617fb3e2f7886272d26ff), GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1e8c2d419c2e/disk-30d27271.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9e8a728a72a9/vmlinux-30d27271.xz
kernel image: https://storage.googleapis.com/syzbot-assets/89f71c80c707/bzImage-30d27271.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+14d9e7602ebdf7ec0a60@syzkaller.appspotmail.com

=====================================================
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: 3530 Comm: kworker/u4:7 Not tainted 6.1.0-rc8-syzkaller-64144-g30d2727189c5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Workqueue: btrfs-delalloc btrfs_work_helper
=====================================================


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