Re: [syzbot] KMSAN: kernel-infoleak in ucma_init_qp_attr

[Leon Romanovsky]

On Tue, Jan 04, 2022 at 02:03:17AM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    81c325bbf94e kmsan: hooks: do not check memory in kmsan_in..
> git tree:       https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=10c4260db00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2d8b9a11641dc9aa
> dashboard link: https://syzkaller.appspot.com/bug?extid=6d532fa8f9463da290bc
> compiler:       clang version 14.0.0 (/usr/local/google/src/llvm-git-monorepo 2b554920f11c8b763cd9ed9003f4e19b919b8e1f), GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: i386
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+6d532fa8f9463da290bc@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> =====================================================
> BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:121 [inline]
> BUG: KMSAN: kernel-infoleak in _copy_to_user+0x1c9/0x270 lib/usercopy.c:33
>  instrument_copy_to_user include/linux/instrumented.h:121 [inline]
>  _copy_to_user+0x1c9/0x270 lib/usercopy.c:33
>  copy_to_user include/linux/uaccess.h:209 [inline]
>  ucma_init_qp_attr+0x8c7/0xb10 drivers/infiniband/core/ucma.c:1242
>  ucma_write+0x637/0x6c0 drivers/infiniband/core/ucma.c:1732
>  vfs_write+0x8ce/0x2030 fs/read_write.c:588
>  ksys_write+0x28b/0x510 fs/read_write.c:643
>  __do_sys_write fs/read_write.c:655 [inline]
>  __se_sys_write fs/read_write.c:652 [inline]
>  __ia32_sys_write+0xdb/0x120 fs/read_write.c:652
>  do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline]
>  __do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180
>  do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205
>  do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248
>  entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> 
> Local variable resp created at:
>  ucma_init_qp_attr+0xa4/0xb10 drivers/infiniband/core/ucma.c:1214
>  ucma_write+0x637/0x6c0 drivers/infiniband/core/ucma.c:1732
> 
> Bytes 40-59 of 144 are uninitialized
> Memory access of size 144 starts at ffff888167523b00
> Data copied to user address 0000000020000100
> 
> CPU: 1 PID: 25910 Comm: syz-executor.1 Not tainted 5.16.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> =====================================================

We are not clearing GRH fields in ib_copy_ah_attr_to_user() if dst->is_global is not set.
I'm testing the fix now and will post the patch after it will pass CI.

Thanks

> 
> 
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