KMSAN: kernel-infoleak in video_usercopy (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    8bbbc5cf kmsan: don't compile memmove
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=178f51b5e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cd0e9a6b0e555cc3
dashboard link: https://syzkaller.appspot.com/bug?extid=c67f8c1e31d62912ff2f
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f39f95e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14c423d9e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c67f8c1e31d62912ff2f@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
BUG: KMSAN: kernel-infoleak in kmsan_copy_to_user+0x81/0x90 mm/kmsan/kmsan_hooks.c:253
CPU: 1 PID: 11474 Comm: syz-executor301 Not tainted 5.6.0-rc2-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+0x1c9/0x220 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
 kmsan_internal_check_memory+0x238/0x3d0 mm/kmsan/kmsan.c:423
 kmsan_copy_to_user+0x81/0x90 mm/kmsan/kmsan_hooks.c:253
 _copy_to_user+0x15a/0x1f0 lib/usercopy.c:33
 copy_to_user include/linux/uaccess.h:174 [inline]
 video_put_user drivers/media/v4l2-core/v4l2-ioctl.c:3165 [inline]
 video_usercopy+0x248c/0x2b50 drivers/media/v4l2-core/v4l2-ioctl.c:3264
 video_ioctl2+0x9f/0xb0 drivers/media/v4l2-core/v4l2-ioctl.c:3274
 v4l2_ioctl+0x23f/0x270 drivers/media/v4l2-core/v4l2-dev.c:360
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl fs/ioctl.c:763 [inline]
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl+0x2e9/0x410 fs/ioctl.c:770
 __x64_sys_ioctl+0x4a/0x70 fs/ioctl.c:770
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x440289
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe00ee4fc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440289
RDX: 00000000200000c0 RSI: 00000000c050560f RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b10
R13: 0000000000401ba0 R14: 0000000000000000 R15: 0000000000000000

Local variable ----vb32.i@video_usercopy created at:
 video_put_user drivers/media/v4l2-core/v4l2-ioctl.c:3149 [inline]
 video_usercopy+0x20bf/0x2b50 drivers/media/v4l2-core/v4l2-ioctl.c:3264
 video_put_user drivers/media/v4l2-core/v4l2-ioctl.c:3149 [inline]
 video_usercopy+0x20bf/0x2b50 drivers/media/v4l2-core/v4l2-ioctl.c:3264

Bytes 52-55 of 80 are uninitialized
Memory access of size 80 starts at ffffa88f81563ce0
Data copied to user address 00000000200000c0
=====================================================


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