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Date:   Mon, 07 Nov 2022 01:10:43 -0800
Message-ID: <00000000000058d01705ecddccb0@google.com>
Subject: [syzbot] KMSAN: uninit-value in pagecache_write
From:   syzbot <syzbot+9767be679ef5016b6082@syzkaller.appspotmail.com>
To:     adilger.kernel@dilger.ca, glider@google.com,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, tytso@mit.edu
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Hello,

syzbot found the following issue on:

HEAD commit:    968c2729e576 x86: kmsan: fix comment in kmsan_shadow.c
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=11d01ad6880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=131312b26465c190
dashboard link: https://syzkaller.appspot.com/bug?extid=9767be679ef5016b6082
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/c78ce21b953f/disk-968c2729.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/22868d826804/vmlinux-968c2729.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9767be679ef5016b6082@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in pagecache_write+0x655/0x720 fs/ext4/verity.c:91
 pagecache_write+0x655/0x720 fs/ext4/verity.c:91
 ext4_write_merkle_tree_block+0x84/0xa0 fs/ext4/verity.c:389
 build_merkle_tree_level+0x972/0x1250 fs/verity/enable.c:121
 build_merkle_tree fs/verity/enable.c:182 [inline]
 enable_verity+0xede/0x1920 fs/verity/enable.c:268
 fsverity_ioctl_enable+0x895/0xab0 fs/verity/enable.c:392
 __ext4_ioctl fs/ext4/ioctl.c:1572 [inline]
 ext4_ioctl+0x26dd/0x8c50 fs/ext4/ioctl.c:1606
 ext4_compat_ioctl+0x702/0x800 fs/ext4/ioctl.c:1682
 __do_compat_sys_ioctl fs/ioctl.c:968 [inline]
 __se_compat_sys_ioctl+0x781/0xfa0 fs/ioctl.c:910
 __ia32_compat_sys_ioctl+0x8f/0xd0 fs/ioctl.c:910
 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
 __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178
 do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:203
 do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:246
 entry_SYSENTER_compat_after_hwframe+0x70/0x82

Local variable fsdata created at:
 pagecache_write+0x21c/0x720 fs/ext4/verity.c:85
 ext4_write_merkle_tree_block+0x84/0xa0 fs/ext4/verity.c:389

CPU: 1 PID: 15121 Comm: syz-executor.3 Not tainted 6.0.0-rc5-syzkaller-48543-g968c2729e576 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
=====================================================


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