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From:   Alexander Potapenko <glider@google.com>
Date:   Mon, 21 Sep 2020 12:10:05 +0200
Message-ID: <CAG_fn=VnujTeKg9r+b8VoTGCs4OdwR0eHj0+HHtn5UzePy3EmA@mail.gmail.com>
Subject: Re: KMSAN: uninit-value in search_by_key
To:     syzbot <syzbot+d94d02749498bb7bab4b@syzkaller.appspotmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        alex.shi@linux.alibaba.com, jack@suse.cz,
        LKML <linux-kernel@vger.kernel.org>,
        reiserfs-devel@vger.kernel.org,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        yeyunfeng@huawei.com, zhengbin13@huawei.com
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On Mon, Sep 21, 2020 at 12:02 PM syzbot
<syzbot+d94d02749498bb7bab4b@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    c5a13b33 kmsan: clang-format core
> git tree:       https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=173525ab900000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=20f149ad694ba4be
> dashboard link: https://syzkaller.appspot.com/bug?extid=d94d02749498bb7bab4b
> compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> userspace arch: i386
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d94d02749498bb7bab4b@syzkaller.appspotmail.com
>
> =====================================================
> BUG: KMSAN: uninit-value in comp_keys fs/reiserfs/stree.c:83 [inline]
> BUG: KMSAN: uninit-value in bin_search fs/reiserfs/stree.c:173 [inline]
> BUG: KMSAN: uninit-value in search_by_key+0x2c57/0x60e0 fs/reiserfs/stree.c:743
> CPU: 1 PID: 28395 Comm: syz-executor.4 Not tainted 5.9.0-rc4-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x21c/0x280 lib/dump_stack.c:118
>  kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:122
>  __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:219
>  comp_keys fs/reiserfs/stree.c:83 [inline]
>  bin_search fs/reiserfs/stree.c:173 [inline]
>  search_by_key+0x2c57/0x60e0 fs/reiserfs/stree.c:743
>  reiserfs_read_locked_inode+0x1fc/0x3260 fs/reiserfs/inode.c:1561
>  reiserfs_fill_super+0x2c00/0x6170 fs/reiserfs/super.c:2081
>  mount_bdev+0x622/0x910 fs/super.c:1417
>  get_super_block+0xc9/0xe0 fs/reiserfs/super.c:2606
>  legacy_get_tree+0x163/0x2e0 fs/fs_context.c:592
>  vfs_get_tree+0xd8/0x5d0 fs/super.c:1547
>  do_new_mount fs/namespace.c:2875 [inline]
>  path_mount+0x3d1a/0x5d40 fs/namespace.c:3192
>  do_mount+0x1c6/0x220 fs/namespace.c:3205
>  __do_compat_sys_mount fs/compat.c:122 [inline]
>  __se_compat_sys_mount+0x7b5/0xaa0 fs/compat.c:89
>  __ia32_compat_sys_mount+0x62/0x80 fs/compat.c:89
>  do_syscall_32_irqs_on arch/x86/entry/common.c:80 [inline]
>  __do_fast_syscall_32+0x129/0x180 arch/x86/entry/common.c:139
>  do_fast_syscall_32+0x6a/0xc0 arch/x86/entry/common.c:162
>  do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:205
>  entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> RIP: 0023:0xf7fea549
> Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
> RSP: 002b:00000000f55e3f20 EFLAGS: 00000292 ORIG_RAX: 0000000000000015
> RAX: ffffffffffffffda RBX: 00000000f55e3f7c RCX: 0000000020000100
> RDX: 0000000020000000 RSI: 0000000000000000 RDI: 00000000f55e3fbc
> RBP: 00000000f55e3f7c R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>
> Local variable ----key@reiserfs_read_locked_inode created at:
>  reiserfs_read_locked_inode+0xb4/0x3260 fs/reiserfs/inode.c:1544
>  reiserfs_read_locked_inode+0xb4/0x3260 fs/reiserfs/inode.c:1544
> =====================================================
>

Looks like reiserfs_read_locked_inode() fails to initialize cpu_key->key_length.
Could someone please take a look?