[syzbot] [kernel?] KMSAN: kernel-infoleak-after-free in copy_siginfo_to_user (2)

[syzbot]

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+cfc087...@syzkaller.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
=====================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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If the bug is already fixed, let syzbot know by replying with:
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If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 861deac3b092 Linux 6.7-rc7
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15826ec9e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3

dashboard link: https://syzkaller.appspot.com/bug?extid=cfc08744435c4cf94a40
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17ea5231e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0ea60ee8ed32/disk-861deac3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6d69fdc33021/vmlinux-861deac3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f0158750d452/bzImage-861deac3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cfc087...@syzkaller.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:3374
ptrace_request+0xfa6/0x36d0 kernel/ptrace.c:1066
arch_ptrace+0x435/0x680 arch/x86/kernel/ptrace.c:848
__do_sys_ptrace kernel/ptrace.c:1305 [inline]
__se_sys_ptrace+0x2d8/0x750 kernel/ptrace.c:1278
__x64_sys_ptrace+0xbd/0x110 kernel/ptrace.c:1278
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was stored to memory at:
copy_siginfo include/linux/signal.h:17 [inline]

ptrace_getsiginfo kernel/ptrace.c:705 [inline]
ptrace_request+0xf32/0x36d0 kernel/ptrace.c:1064
arch_ptrace+0x435/0x680 arch/x86/kernel/ptrace.c:848
__do_sys_ptrace kernel/ptrace.c:1305 [inline]
__se_sys_ptrace+0x2d8/0x750 kernel/ptrace.c:1278
__x64_sys_ptrace+0xbd/0x110 kernel/ptrace.c:1278
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

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:2784

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+0x50/0x110 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x63/0x6b

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+0x66f/0x1250 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:2784

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+0x50/0x110 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Bytes 12-15 of 48 are uninitialized

Memory access of size 48 starts at ffff888115d6bc80
Data copied to user address 00000000016164e0

CPU: 1 PID: 5004 Comm: strace-static-x Not tainted 6.7.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
=====================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[Edward Adam Davis]

please test kernel-infoleak-after-free in copy_siginfo_to_user

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 861deac3b092

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index d8b5e13a2229..8bd346b10c6e 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1033,7 +1033,7 @@ int ptrace_request(struct task_struct *child, long request,
{
bool seized = child->ptrace & PT_SEIZED;
int ret = -EIO;
- kernel_siginfo_t siginfo, *si;
+ kernel_siginfo_t siginfo, *si, *psiginfo;
void __user *datavp = (void __user *) data;
unsigned long __user *datalp = datavp;
unsigned long flags;
@@ -1061,9 +1061,13 @@ int ptrace_request(struct task_struct *child, long request,
break;

case PTRACE_GETSIGINFO:
- ret = ptrace_getsiginfo(child, &siginfo);
+ psiginfo = kvmalloc(sizeof(kernel_siginfo_t), GFP_KERNEL);
+ if (!psiginfo)
+ break;
+ ret = ptrace_getsiginfo(child, psiginfo);
if (!ret)
- ret = copy_siginfo_to_user(datavp, &siginfo);
+ ret = copy_siginfo_to_user(datavp, psiginfo);
+ kvfree(psiginfo);
break;

case PTRACE_SETSIGINFO:

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+cfc087...@syzkaller.appspotmail.com

Tested on:

commit: 861deac3 Linux 6.7-rc7
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=13c1bf11e80000

kernel config: https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
dashboard link: https://syzkaller.appspot.com/bug?extid=cfc08744435c4cf94a40
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13310ef9e80000

Note: testing is done by a robot and is best-effort only.

[Edward Adam Davis]

To avoid kernel memory leakage into user space, memory should be manually
allocated instead of using memory from the kernel stack.

Reported-and-tested-by: syzbot+cfc087...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
kernel/ptrace.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--
2.43.0

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 70293240c5ce Merge tag 'timers-urgent-2024-03-23' of git:/..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=139071be180000
kernel config: https://syzkaller.appspot.com/x/.config?x=e6bd769cb793b98a

dashboard link: https://syzkaller.appspot.com/bug?extid=cfc08744435c4cf94a40
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14694231180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15846fc1180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0de52742d0b8/disk-70293240.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f304697881bf/vmlinux-70293240.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2b9d8a9376f0/bzImage-70293240.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cfc087...@syzkaller.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/0x110 lib/usercopy.c:40
instrument_copy_to_user include/linux/instrumented.h:114 [inline]
_copy_to_user+0xbc/0x110 lib/usercopy.c:40
copy_to_user include/linux/uaccess.h:191 [inline]
copy_siginfo_to_user+0x40/0x130 kernel/signal.c:3380
ptrace_request+0xfa7/0x36e0 kernel/ptrace.c:1046
arch_ptrace+0x43b/0x680 arch/x86/kernel/ptrace.c:848
__do_sys_ptrace kernel/ptrace.c:1285 [inline]
__se_sys_ptrace+0x2d8/0x760 kernel/ptrace.c:1258
__x64_sys_ptrace+0xbd/0x110 kernel/ptrace.c:1258
do_syscall_64+0xd5/0x1f0
entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was stored to memory at:

copy_siginfo include/linux/signal.h:18 [inline]
ptrace_getsiginfo kernel/ptrace.c:685 [inline]
ptrace_request+0xf33/0x36e0 kernel/ptrace.c:1044
arch_ptrace+0x43b/0x680 arch/x86/kernel/ptrace.c:848
__do_sys_ptrace kernel/ptrace.c:1285 [inline]
__se_sys_ptrace+0x2d8/0x760 kernel/ptrace.c:1258
__x64_sys_ptrace+0xbd/0x110 kernel/ptrace.c:1258
do_syscall_64+0xd5/0x1f0
entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was stored to memory at:

copy_siginfo include/linux/signal.h:18 [inline]
collect_signal kernel/signal.c:587 [inline]
__dequeue_signal+0x501/0xad0 kernel/signal.c:616
dequeue_signal+0x14b/0xb20 kernel/signal.c:639
get_signal+0xb46/0x2d00 kernel/signal.c:2790
arch_do_signal_or_restart+0x53/0xcb0 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x5d/0x160 kernel/entry/common.c:218
do_syscall_64+0xe4/0x1f0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was created at:
slab_free_hook mm/slub.c:2073 [inline]
slab_free mm/slub.c:4280 [inline]
kmem_cache_free+0x257/0xa80 mm/slub.c:4344
__sigqueue_free kernel/signal.c:451 [inline]
collect_signal kernel/signal.c:594 [inline]
__dequeue_signal+0xa58/0xad0 kernel/signal.c:616
dequeue_signal+0x14b/0xb20 kernel/signal.c:639
get_signal+0xb46/0x2d00 kernel/signal.c:2790
arch_do_signal_or_restart+0x53/0xcb0 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x5d/0x160 kernel/entry/common.c:218
do_syscall_64+0xe4/0x1f0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x6d/0x75

Bytes 12-15 of 48 are uninitialized

Memory access of size 48 starts at ffff8881240cfc60
Data copied to user address 0000000014dcf540

CPU: 1 PID: 5012 Comm: strace-static-x Not tainted 6.8.0-syzkaller-13213-g70293240c5ce #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024