Re: KMSAN: kernel-infoleak in move_addr_to_user (4)

[Jakub Kicinski]

Looks like a AF_CAN socket:

r0 = socket(0x1d, 0x2, 0x6)
getsockname$packet(r0, &(0x7f0000000100)={0x11, 0x0, 0x0, 0x1, 0x0, 0x6, @broadcast}, &(0x7f0000000000)=0x14)


On Sun, 10 Jan 2021 02:19:15 -0800 syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    73d62e81 kmsan: random: prevent boot-time reports in _mix_..
> git tree:       https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=15c8b8c7500000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2cdf4151c9653e32
> dashboard link: https://syzkaller.appspot.com/bug?extid=057884e2f453e8afebc8
> compiler:       clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=101520c7500000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100b8f4f500000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+057884e2f453e8afebc8@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> =====================================================
> BUG: KMSAN: kernel-infoleak in kmsan_copy_to_user+0x9c/0xb0 mm/kmsan/kmsan_hooks.c:249
> CPU: 0 PID: 8245 Comm: syz-executor868 Not tainted 5.10.0-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:118
>  kmsan_internal_check_memory+0x202/0x520 mm/kmsan/kmsan.c:402
>  kmsan_copy_to_user+0x9c/0xb0 mm/kmsan/kmsan_hooks.c:249
>  instrument_copy_to_user include/linux/instrumented.h:121 [inline]
>  _copy_to_user+0x1af/0x270 lib/usercopy.c:33
>  copy_to_user include/linux/uaccess.h:209 [inline]
>  move_addr_to_user+0x3a2/0x640 net/socket.c:237
>  __sys_getsockname+0x407/0x5d0 net/socket.c:1906
>  __do_sys_getsockname net/socket.c:1917 [inline]
>  __se_sys_getsockname+0x91/0xb0 net/socket.c:1914
>  __x64_sys_getsockname+0x4a/0x70 net/socket.c:1914
>  do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x441219
> Code: e8 fc ab 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 1b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffe3c24eaf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000033
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441219
> RDX: 0000000020000000 RSI: 0000000020000100 RDI: 0000000000000003
> RBP: 00000000006cb018 R08: 00000000004002c8 R09: 00000000004002c8
> R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000401fc0
> R13: 0000000000402050 R14: 0000000000000000 R15: 0000000000000000
> 
> Local variable ----address@__sys_getsockname created at:
>  __sys_getsockname+0x91/0x5d0 net/socket.c:1891
>  __sys_getsockname+0x91/0x5d0 net/socket.c:1891
> 
> Bytes 2-3 of 20 are uninitialized
> Memory access of size 20 starts at ffff888124bbbdf0
> Data copied to user address 0000000020000100
> =====================================================
> 
> 
> ---
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