KMSAN: kernel-infoleak in copy_siginfo_to_user (2)

From: syzbot
Date: Sun May 12 2019 - 06:08:35 EST


syzbot found the following crash on:

HEAD commit: d062d017 usb-fuzzer: main usb gadget fuzzer driver
git tree: kmsan
console output:
kernel config:
dashboard link:
compiler: clang version 9.0.0 (/home/glider/llvm/clang 06d00afa61eef8f7f501ebdb4e8612ea43ec2d78)
syz repro:
C reproducer:

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0d602a1b0d8c95bdf299@xxxxxxxxxxxxxxxxxxxxxxxxx

ptrace attach of "./syz-executor353086472"[10278] was attempted by "./syz-executor353086472"[10279]
ptrace attach of "./syz-executor353086472"[10280] was attempted by "./syz-executor353086472"[10281]
ptrace attach of "./syz-executor353086472"[10282] was attempted by "./syz-executor353086472"[10283]
BUG: KMSAN: kernel-infoleak in _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
CPU: 1 PID: 10284 Comm: syz-executor353 Not tainted 5.1.0-rc7+ #5
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+0x191/0x1f0 lib/dump_stack.c:113
kmsan_report+0x130/0x2a0 mm/kmsan/kmsan.c:619
kmsan_internal_check_memory+0x974/0xa80 mm/kmsan/kmsan.c:713
kmsan_copy_to_user+0xa9/0xb0 mm/kmsan/kmsan_hooks.c:492
_copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
copy_to_user include/linux/uaccess.h:174 [inline]
copy_siginfo_to_user+0x80/0x160 kernel/signal.c:3059
ptrace_peek_siginfo kernel/ptrace.c:742 [inline]
ptrace_request+0x24bd/0x2950 kernel/ptrace.c:913
arch_ptrace+0x9fa/0x1090 arch/x86/kernel/ptrace.c:868
__do_sys_ptrace kernel/ptrace.c:1155 [inline]
__se_sys_ptrace+0x2b9/0x7b0 kernel/ptrace.c:1120
__x64_sys_ptrace+0x56/0x70 kernel/ptrace.c:1120
do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
RIP: 0033:0x441cc9
Code: e8 bc e6 ff ff 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 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00000000007efdd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000065
RAX: ffffffffffffffda RBX: 0000000000000063 RCX: 0000000000441cc9
RDX: 00000000200000c0 RSI: 0000000000000007 RDI: 0000000000004209
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000716000 R11: 0000000000000246 R12: 0000000000000002
R13: 0000000000402a00 R14: 0000000000000000 R15: 0000000000000000

Local variable description: ----info.i@ptrace_request
Variable was created at:
ptrace_peek_siginfo kernel/ptrace.c:714 [inline]
ptrace_request+0x2161/0x2950 kernel/ptrace.c:913
arch_ptrace+0x9fa/0x1090 arch/x86/kernel/ptrace.c:868

Bytes 0-47 of 48 are uninitialized
Memory access of size 48 starts at ffff8880a902fd70
Data copied to user address 0000000000716000

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