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Date:   Mon, 31 Aug 2020 03:28:22 -0700
Message-ID: <000000000000a24fa705ae29dc6c@google.com>
Subject: KMSAN: kernel-infoleak in scsi_cmd_ioctl
From:   syzbot <syzbot+85433a479a646a064ab3@syzkaller.appspotmail.com>
To:     axboe@kernel.dk, glider@google.com, linux-block@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:    3b3ea602 x86: add failure injection to get/put/clear_user
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=14d89966900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3afe005fb99591f
dashboard link: https://syzkaller.appspot.com/bug?extid=85433a479a646a064ab3
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+85433a479a646a064ab3@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: kernel-infoleak in kmsan_copy_to_user+0x81/0x90 mm/kmsan/kmsan_hooks.c:253
CPU: 1 PID: 12272 Comm: syz-executor.3 Not tainted 5.8.0-rc5-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:121
 kmsan_internal_check_memory+0x238/0x3d0 mm/kmsan/kmsan.c:423
 kmsan_copy_to_user+0x81/0x90 mm/kmsan/kmsan_hooks.c:253
 instrument_copy_to_user include/linux/instrumented.h:91 [inline]
 _copy_to_user+0x18e/0x260 lib/usercopy.c:33
 scsi_put_cdrom_generic_arg include/linux/uaccess.h:170 [inline]
 scsi_cdrom_send_packet block/scsi_ioctl.c:770 [inline]
 scsi_cmd_ioctl+0x2422/0x25a0 block/scsi_ioctl.c:827
 scsi_cmd_blk_ioctl+0x1f6/0x240 block/scsi_ioctl.c:876
 sd_ioctl_common+0x50a/0x5c0 drivers/scsi/sd.c:1531
 sd_compat_ioctl+0xc5/0x220 drivers/scsi/sd.c:1733
 compat_blkdev_ioctl+0x74b/0x1200 block/ioctl.c:691
 __do_compat_sys_ioctl fs/ioctl.c:847 [inline]
 __se_compat_sys_ioctl+0x55f/0x1100 fs/ioctl.c:798
 __ia32_compat_sys_ioctl+0x4a/0x70 fs/ioctl.c:798
 do_syscall_32_irqs_on arch/x86/entry/common.c:430 [inline]
 __do_fast_syscall_32+0x2af/0x480 arch/x86/entry/common.c:477
 do_fast_syscall_32+0x6b/0xd0 arch/x86/entry/common.c:505
 do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:554
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7fae549
Code: Bad RIP value.
RSP: 002b:00000000f55a80cc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000005393
RDX: 0000000020002000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Local variable ----cgc32.i42.i@scsi_cmd_ioctl created at:
 scsi_put_cdrom_generic_arg block/scsi_ioctl.c:695 [inline]
 scsi_cdrom_send_packet block/scsi_ioctl.c:770 [inline]
 scsi_cmd_ioctl+0x2257/0x25a0 block/scsi_ioctl.c:827
 scsi_put_cdrom_generic_arg block/scsi_ioctl.c:695 [inline]
 scsi_cdrom_send_packet block/scsi_ioctl.c:770 [inline]
 scsi_cmd_ioctl+0x2257/0x25a0 block/scsi_ioctl.c:827

Bytes 29-31 of 44 are uninitialized
Memory access of size 44 starts at ffff8881c5bfbaa0
Data copied to user address 0000000020002000
=====================================================


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