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Date:   Wed, 30 Aug 2023 00:49:53 -0700
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Subject: [syzbot] [btrfs?] UBSAN: array-index-out-of-bounds in FSE_decompress_wksp_body_bmi2
From:   syzbot <syzbot+1f2eb3e8cd123ffce499@syzkaller.appspotmail.com>
To:     clm@fb.com, dsterba@suse.com, josef@toxicpanda.com,
        linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
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Hello,

syzbot found the following issue on:

HEAD commit:    382d4cd18475 lib/clz_ctz.c: Fix __clzdi2() and __ctzdi2() ..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15979833a80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1b32f62c755c3a9c
dashboard link: https://syzkaller.appspot.com/bug?extid=1f2eb3e8cd123ffce499
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/57260ac283ce/disk-382d4cd1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8be20b71d903/vmlinux-382d4cd1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/518fe2320c33/bzImage-382d4cd1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1f2eb3e8cd123ffce499@syzkaller.appspotmail.com

================================================================================
UBSAN: array-index-out-of-bounds in lib/zstd/common/fse_decompress.c:345:30
index 33 is out of range for type 'FSE_DTable[1]' (aka 'unsigned int[1]')
CPU: 0 PID: 2895 Comm: kworker/u4:7 Not tainted 6.5.0-rc7-syzkaller-00164-g382d4cd18475 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Workqueue: btrfs-endio btrfs_end_bio_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 ubsan_epilogue lib/ubsan.c:217 [inline]
 __ubsan_handle_out_of_bounds+0x11c/0x150 lib/ubsan.c:348
 FSE_decompress_wksp_body lib/zstd/common/fse_decompress.c:345 [inline]
 FSE_decompress_wksp_body_bmi2+0x2e8/0x3790 lib/zstd/common/fse_decompress.c:370
 FSE_decompress_wksp_bmi2+0xc7/0x3670 lib/zstd/common/fse_decompress.c:378
 HUF_readStats_body lib/zstd/common/entropy_common.c:289 [inline]
 HUF_readStats_body_bmi2+0xba/0x620 lib/zstd/common/entropy_common.c:340
 HUF_readDTableX1_wksp_bmi2+0x161/0x2740 lib/zstd/decompress/huf_decompress.c:353
 HUF_decompress1X1_DCtx_wksp_bmi2+0x4e/0xe0 lib/zstd/decompress/huf_decompress.c:1693
 ZSTD_decodeLiteralsBlock+0x1009/0x1560 lib/zstd/decompress/zstd_decompress_block.c:195
 ZSTD_decompressBlock_internal+0x106/0xacc0 lib/zstd/decompress/zstd_decompress_block.c:1995
 ZSTD_decompressContinue+0x571/0x1690 lib/zstd/decompress/zstd_decompress.c:1184
 ZSTD_decompressContinueStream lib/zstd/decompress/zstd_decompress.c:1855 [inline]
 ZSTD_decompressStream+0x208f/0x3080 lib/zstd/decompress/zstd_decompress.c:2036
 zstd_decompress_bio+0x22b/0x570 fs/btrfs/zstd.c:573
 compression_decompress_bio fs/btrfs/compression.c:131 [inline]
 btrfs_decompress_bio fs/btrfs/compression.c:930 [inline]
 end_compressed_bio_read+0x145/0x400 fs/btrfs/compression.c:178
 btrfs_check_read_bio+0x138f/0x19b0 fs/btrfs/bio.c:324
 process_one_work+0x92c/0x12c0 kernel/workqueue.c:2600
 worker_thread+0xa63/0x1210 kernel/workqueue.c:2751
 kthread+0x2b8/0x350 kernel/kthread.c:389
 ret_from_fork+0x2e/0x60 arch/x86/kernel/process.c:145
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
 </TASK>
================================================================================


---
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