[syzbot] [nfs?] KMSAN: kernel-infoleak in sys_name_to_handle_at (4)

[syzbot] [nfs?] KMSAN: kernel-infoleak in sys_name_to_handle_at (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    861deac3b092 Linux 6.7-rc7
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=155d9131e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
dashboard link: https://syzkaller.appspot.com/bug?extid=09b349b3066c2e0b1e96
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=16cefdc9e80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=164fe7e9e80000

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
mounted in repro: https://storage.googleapis.com/syzbot-assets/bb450f076a10/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+09b349b3066c2e0b1e96@syzkaller.appspotmail.com

         option from the mount to silence this warning.
=======================================================
=====================================================
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak 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]
 do_sys_name_to_handle fs/fhandle.c:73 [inline]
 __do_sys_name_to_handle_at fs/fhandle.c:112 [inline]
 __se_sys_name_to_handle_at+0x949/0xb10 fs/fhandle.c:94
 __x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94
 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 created at:
 slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
 slab_alloc_node mm/slub.c:3478 [inline]
 __kmem_cache_alloc_node+0x5c9/0x970 mm/slub.c:3517
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc+0x121/0x3c0 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 do_sys_name_to_handle fs/fhandle.c:39 [inline]
 __do_sys_name_to_handle_at fs/fhandle.c:112 [inline]
 __se_sys_name_to_handle_at+0x441/0xb10 fs/fhandle.c:94
 __x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94
 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

Bytes 18-19 of 20 are uninitialized
Memory access of size 20 starts at ffff888128a46380
Data copied to user address 0000000020000240

CPU: 0 PID: 5006 Comm: syz-executor975 Not tainted 6.7.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
=====================================================


---
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Re: [syzbot] [nfs?] KMSAN: kernel-infoleak in sys_name_to_handle_at (4)

[Chuck Lever III]

> On Jan 14, 2024, at 5:14 AM, syzbot <syzbot+09b349b3066c2e0b1e96@syzkaller.appspotmail.com> wrote:
> 
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    861deac3b092 Linux 6.7-rc7
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=155d9131e80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
> dashboard link: https://syzkaller.appspot.com/bug?extid=09b349b3066c2e0b1e96
> 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=16cefdc9e80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=164fe7e9e80000
> 
> 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
> mounted in repro: https://storage.googleapis.com/syzbot-assets/bb450f076a10/mount_0.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+09b349b3066c2e0b1e96@syzkaller.appspotmail.com
> 
>         option from the mount to silence this warning.
> =======================================================
> =====================================================
> BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
> BUG: KMSAN: kernel-infoleak 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]
> do_sys_name_to_handle fs/fhandle.c:73 [inline]
> __do_sys_name_to_handle_at fs/fhandle.c:112 [inline]
> __se_sys_name_to_handle_at+0x949/0xb10 fs/fhandle.c:94
> __x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94
> 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 created at:
> slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
> slab_alloc_node mm/slub.c:3478 [inline]
> __kmem_cache_alloc_node+0x5c9/0x970 mm/slub.c:3517
> __do_kmalloc_node mm/slab_common.c:1006 [inline]
> __kmalloc+0x121/0x3c0 mm/slab_common.c:1020
> kmalloc include/linux/slab.h:604 [inline]
> do_sys_name_to_handle fs/fhandle.c:39 [inline]
> __do_sys_name_to_handle_at fs/fhandle.c:112 [inline]
> __se_sys_name_to_handle_at+0x441/0xb10 fs/fhandle.c:94
> __x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94
> 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
> 
> Bytes 18-19 of 20 are uninitialized
> Memory access of size 20 starts at ffff888128a46380
> Data copied to user address 0000000020000240
> 
> CPU: 0 PID: 5006 Comm: syz-executor975 Not tainted 6.7.0-rc7-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> =====================================================

Hi Amir-

The kmalloc() at fs/fhandle.c:39 could be made a kzalloc().

But I wonder if those uninitialized bytes in the file_handle
buffer are actually a logic bug in do_sys_name_to_handle().


--
Chuck Lever

Re: [syzbot] [nfs?] KMSAN: kernel-infoleak in sys_name_to_handle_at (4)

[Amir Goldstein]

On Tue, Jan 16, 2024 at 5:08 PM Chuck Lever III <chuck.lever@oracle.com> wrote:
>
>
>
> > On Jan 14, 2024, at 5:14 AM, syzbot <syzbot+09b349b3066c2e0b1e96@syzkaller.appspotmail.com> wrote:
> >
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    861deac3b092 Linux 6.7-rc7
> > git tree:       upstream
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=155d9131e80000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
> > dashboard link: https://syzkaller.appspot.com/bug?extid=09b349b3066c2e0b1e96
> > 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=16cefdc9e80000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=164fe7e9e80000
> >
> > 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
> > mounted in repro: https://storage.googleapis.com/syzbot-assets/bb450f076a10/mount_0.gz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+09b349b3066c2e0b1e96@syzkaller.appspotmail.com
> >
> >         option from the mount to silence this warning.
> > =======================================================
> > =====================================================
> > BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
> > BUG: KMSAN: kernel-infoleak 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]
> > do_sys_name_to_handle fs/fhandle.c:73 [inline]
> > __do_sys_name_to_handle_at fs/fhandle.c:112 [inline]
> > __se_sys_name_to_handle_at+0x949/0xb10 fs/fhandle.c:94
> > __x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94
> > 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 created at:
> > slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
> > slab_alloc_node mm/slub.c:3478 [inline]
> > __kmem_cache_alloc_node+0x5c9/0x970 mm/slub.c:3517
> > __do_kmalloc_node mm/slab_common.c:1006 [inline]
> > __kmalloc+0x121/0x3c0 mm/slab_common.c:1020
> > kmalloc include/linux/slab.h:604 [inline]
> > do_sys_name_to_handle fs/fhandle.c:39 [inline]
> > __do_sys_name_to_handle_at fs/fhandle.c:112 [inline]
> > __se_sys_name_to_handle_at+0x441/0xb10 fs/fhandle.c:94
> > __x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94
> > 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
> >
> > Bytes 18-19 of 20 are uninitialized
> > Memory access of size 20 starts at ffff888128a46380
> > Data copied to user address 0000000020000240
> >
> > CPU: 0 PID: 5006 Comm: syz-executor975 Not tainted 6.7.0-rc7-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> > =====================================================
>
> Hi Amir-
>
> The kmalloc() at fs/fhandle.c:39 could be made a kzalloc().
>
> But I wonder if those uninitialized bytes in the file_handle
> buffer are actually a logic bug in do_sys_name_to_handle().
>

I am not sure I understand from the report which bytes are not initialized.
If it's the bytes of the opaque f_handle, then it sounds like a
filesystem (nilfs) bug.

Thanks,
Amir.

Re: [syzbot] [syzbot] [nfs?] KMSAN: kernel-infoleak in sys_name_to_handle_at (4)

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [syzbot] [nfs?] KMSAN: kernel-infoleak in sys_name_to_handle_at (4)
Author: n.zhandarovich@fintech.ru

Try using kzalloc() instead of kmalloc() in do_sys_name_to_handle()

#syz test: https://github.com/google/kmsan.git master

---
 fs/fhandle.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fhandle.c b/fs/fhandle.c
index 18b3ba8dc8ea..57a12614addf 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -36,7 +36,7 @@ static long do_sys_name_to_handle(const struct path *path,
 	if (f_handle.handle_bytes > MAX_HANDLE_SZ)
 		return -EINVAL;
 
-	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
+	handle = kzalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
 			 GFP_KERNEL);
 	if (!handle)
 		return -ENOMEM;
-- 
2.25.1

Re: [syzbot] [nfs?] KMSAN: kernel-infoleak in sys_name_to_handle_at (4)

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+09b349b3066c2e0b1e96@syzkaller.appspotmail.com

Tested on:

commit:         d1d7f15c DO-NOT-SUBMIT: kmsan: add the kmsan_exceed_ma..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=125bb51be80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4778da307461370c
dashboard link: https://syzkaller.appspot.com/bug?extid=09b349b3066c2e0b1e96
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10f39bfbe80000

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