linux-kernel - [syzbot] [kernel?] KMSAN: kernel-infoleak-after-free in copy_siginfo_to

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Date:   Sat, 21 Oct 2023 11:49:56 -0700
From:   syzbot <syzbot+cfc08744435c4cf94a40@...kaller.appspotmail.com>
To:     linux-kernel@...r.kernel.org, luto@...nel.org,
        peterz@...radead.org, syzkaller-bugs@...glegroups.com,
        tglx@...utronix.de
Subject: [syzbot] [kernel?] KMSAN: kernel-infoleak-after-free in
 copy_siginfo_to_user (2)

Hello,

syzbot found the following issue on:

HEAD commit:    dd72f9c7e512 Merge tag 'spi-fix-v6-6-rc4' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15fd7ae5680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3f3af4cd712401d4
dashboard link: https://syzkaller.appspot.com/bug?extid=cfc08744435c4cf94a40
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/70e48b37a929/disk-dd72f9c7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/60aeb36b39dc/vmlinux-dd72f9c7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/71699a83a138/bzImage-dd72f9c7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cfc08744435c4cf94a40@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: kernel-infoleak-after-free in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak-after-free in _copy_to_user+0xbc/0x100 lib/usercopy.c:40
 instrument_copy_to_user include/linux/instrumented.h:114 [inline]
 _copy_to_user+0xbc/0x100 lib/usercopy.c:40
 copy_to_user include/linux/uaccess.h:191 [inline]
 copy_siginfo_to_user+0x40/0x130 kernel/signal.c:3362
 x64_setup_rt_frame+0x1e74/0x2400 arch/x86/kernel/signal_64.c:197
 setup_rt_frame arch/x86/kernel/signal.c:222 [inline]
 handle_signal arch/x86/kernel/signal.c:266 [inline]
 arch_do_signal_or_restart+0x626/0xca0 arch/x86/kernel/signal.c:311
 exit_to_user_mode_loop+0xe8/0x320 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x163/0x220 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x2a/0x140 kernel/entry/common.c:296
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Uninit was stored to memory at:
 copy_siginfo include/linux/signal.h:17 [inline]
 collect_signal kernel/signal.c:596 [inline]
 __dequeue_signal+0x548/0xa00 kernel/signal.c:625
 dequeue_signal+0x14b/0xb10 kernel/signal.c:648
 get_signal+0xc3f/0x2d10 kernel/signal.c:2772
 arch_do_signal_or_restart+0x53/0xca0 arch/x86/kernel/signal.c:309
 exit_to_user_mode_loop+0xe8/0x320 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x163/0x220 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x2a/0x140 kernel/entry/common.c:296
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Uninit was created at:
 slab_free_hook mm/slub.c:1770 [inline]
 slab_free_freelist_hook mm/slub.c:1826 [inline]
 slab_free mm/slub.c:3809 [inline]
 kmem_cache_free+0x670/0x12a0 mm/slub.c:3831
 __sigqueue_free kernel/signal.c:460 [inline]
 collect_signal kernel/signal.c:603 [inline]
 __dequeue_signal+0x998/0xa00 kernel/signal.c:625
 dequeue_signal+0x14b/0xb10 kernel/signal.c:648
 get_signal+0xc3f/0x2d10 kernel/signal.c:2772
 arch_do_signal_or_restart+0x53/0xca0 arch/x86/kernel/signal.c:309
 exit_to_user_mode_loop+0xe8/0x320 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x163/0x220 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x2a/0x140 kernel/entry/common.c:296
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Bytes 12-15 of 48 are uninitialized
Memory access of size 48 starts at ffff88801301fdb0
Data copied to user address 000000c000e7bbf0

CPU: 0 PID: 5011 Comm: syz-fuzzer Not tainted 6.6.0-rc6-syzkaller-00043-gdd72f9c7e512 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
=====================================================


---
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