On Tue, Mar 16, 2021 at 11:18 AM syzbot <syzbot+142888ffec98ab194...@syzkaller.appspotmail.com> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 29ad81a1 arch/x86: add missing include to sparsemem.h > git tree: https://github.com/google/kmsan.git master > console output: https://syzkaller.appspot.com/x/log.txt?x=102502dcd00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=8b976581f6bd1e7d > dashboard link: https://syzkaller.appspot.com/bug?extid=142888ffec98ab194028 > compiler: Debian clang version 11.0.1-2 > 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+142888ffec98ab194...@syzkaller.appspotmail.com > > ===================================================== > BUG: KMSAN: uninit-value in check_array_args > drivers/media/v4l2-core/v4l2-ioctl.c:3041 [inline] > BUG: KMSAN: uninit-value in video_usercopy+0x1631/0x3d30 > drivers/media/v4l2-core/v4l2-ioctl.c:3315 > CPU: 0 PID: 19595 Comm: syz-executor.4 Not tainted 5.11.0-rc7-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:79 [inline] > dump_stack+0x21c/0x280 lib/dump_stack.c:120 > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 > __msan_warning+0x5f/0xa0 mm/kmsan/kmsan_instr.c:197 > check_array_args drivers/media/v4l2-core/v4l2-ioctl.c:3041 [inline] > video_usercopy+0x1631/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3315 > video_ioctl2+0x9f/0xb0 drivers/media/v4l2-core/v4l2-ioctl.c:3391 > v4l2_ioctl+0x255/0x290 drivers/media/v4l2-core/v4l2-dev.c:360 > v4l2_compat_ioctl32+0x2c6/0x370 > drivers/media/v4l2-core/v4l2-compat-ioctl32.c:1248 > __do_compat_sys_ioctl fs/ioctl.c:842 [inline] > __se_compat_sys_ioctl+0x53d/0x1100 fs/ioctl.c:793 > __ia32_compat_sys_ioctl+0x4a/0x70 fs/ioctl.c:793 > do_syscall_32_irqs_on arch/x86/entry/common.c:79 [inline] > __do_fast_syscall_32+0x102/0x160 arch/x86/entry/common.c:141 > do_fast_syscall_32+0x6a/0xc0 arch/x86/entry/common.c:166 > do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:209 > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c > RIP: 0023:0xf7fec549 > Code: 03 74 c0 01 10 05 03 74 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 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 > 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 > RSP: 002b:00000000f55e65fc EFLAGS: 00000296 ORIG_RAX: 0000000000000036 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000c050565d > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > > Local variable ----sbuf@video_usercopy created at: > video_usercopy+0xaa/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3285 > video_usercopy+0xaa/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3285 > ===================================================== > ===================================================== > BUG: KMSAN: uninit-value in check_fmt+0x864/0x1070 > drivers/media/v4l2-core/v4l2-ioctl.c:963 > CPU: 0 PID: 19595 Comm: syz-executor.4 Tainted: G B > 5.11.0-rc7-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:79 [inline] > dump_stack+0x21c/0x280 lib/dump_stack.c:120 > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 > __msan_warning+0x5f/0xa0 mm/kmsan/kmsan_instr.c:197 > check_fmt+0x864/0x1070 drivers/media/v4l2-core/v4l2-ioctl.c:963 > v4l_prepare_buf+0xbf/0x1d0 drivers/media/v4l2-core/v4l2-ioctl.c:2107 > __video_do_ioctl+0x15cd/0x1d20 drivers/media/v4l2-core/v4l2-ioctl.c:2993 > video_usercopy+0x2313/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3345 > video_ioctl2+0x9f/0xb0 drivers/media/v4l2-core/v4l2-ioctl.c:3391 > v4l2_ioctl+0x255/0x290 drivers/media/v4l2-core/v4l2-dev.c:360 > v4l2_compat_ioctl32+0x2c6/0x370 > drivers/media/v4l2-core/v4l2-compat-ioctl32.c:1248 > __do_compat_sys_ioctl fs/ioctl.c:842 [inline] > __se_compat_sys_ioctl+0x53d/0x1100 fs/ioctl.c:793 > __ia32_compat_sys_ioctl+0x4a/0x70 fs/ioctl.c:793 > do_syscall_32_irqs_on arch/x86/entry/common.c:79 [inline] > __do_fast_syscall_32+0x102/0x160 arch/x86/entry/common.c:141 > do_fast_syscall_32+0x6a/0xc0 arch/x86/entry/common.c:166 > do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:209 > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c > RIP: 0023:0xf7fec549 > Code: 03 74 c0 01 10 05 03 74 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 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 > 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 > RSP: 002b:00000000f55e65fc EFLAGS: 00000296 ORIG_RAX: 0000000000000036 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000c050565d > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > > Local variable ----sbuf@video_usercopy created at: > video_usercopy+0xaa/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3285 > video_usercopy+0xaa/0x3d30 drivers/media/v4l2-core/v4l2-ioctl.c:3285 > =====================================================
I did not get to the very bottom of this, but I looked at this a bit. It seems to be related to some unfortunate interaction of compat syscall and CONFIG_COMPAT_32BIT_TIME. It seems that in this case nothing at all is copied from userspace because cmd gets messed up or something. Perhaps VIDIOC_QUERYBUF is translated into VIDIOC_QUERYBUF_TIME32 instead of VIDIOC_QUERYBUF32_TIME32 and then this gets into compat syscall path and v4l2_compat_get_user does not recognize the command, copies nothing but returns 0. > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkal...@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > -- > You received this message because you are subscribed to the Google Groups > "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to syzkaller-bugs+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/syzkaller-bugs/0000000000005ace4405bda4af71%40google.com.
