Reminder: 2 open syzbot bugs in "security/tomoyo" subsystem

Reminder: 2 open syzbot bugs in "security/tomoyo" subsystem

[Eric Biggers]

[This email was generated by a script.  Let me know if you have any suggestions
to make it better, or if you want it re-generated with the latest status.]

Of the currently open syzbot reports against the upstream kernel, I've manually
marked 2 of them as possibly being bugs in the "security/tomoyo" subsystem. 
I've listed these reports below, sorted by an algorithm that tries to list first
the reports most likely to be still valid, important, and actionable.

If you believe a bug is no longer valid, please close the syzbot report by
sending a '#syz fix', '#syz dup', or '#syz invalid' command in reply to the
original thread, as explained at https://goo.gl/tpsmEJ#status

If you believe I misattributed a bug to the "security/tomoyo" subsystem, please
let me know, and if possible forward the report to the correct people or mailing
list.

Here are the bugs:

--------------------------------------------------------------------------------
Title:              KASAN: use-after-free Read in tomoyo_realpath_from_path
Last occurred:      28 days ago
Reported:           48 days ago
Branches:           Mainline and others
Dashboard link:     https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74
Original thread:    https://lkml.kernel.org/lkml/0000000000004f43fa058a97f4d3@google.com/T/#u

This bug has a syzkaller reproducer only.

The original thread for this bug has received 7 replies; the last was 31 days
ago.

If you fix this bug, please add the following tag to the commit:
    Reported-by: syzbot+0341f6a4d729d4e0acf1@syzkaller.appspotmail.com

If you send any email or patch for this bug, please consider replying to the
original thread.  For the git send-email command to use, or tips on how to reply
if the thread isn't in your mailbox, see the "Reply instructions" at
https://lkml.kernel.org/r/0000000000004f43fa058a97f4d3@google.com

--------------------------------------------------------------------------------
Title:              KASAN: invalid-free in tomoyo_realpath_from_path
Last occurred:      57 days ago
Reported:           56 days ago
Branches:           net-next
Dashboard link:     https://syzkaller.appspot.com/bug?id=e9e5a1d41c3fb5d0f79aeea0e4cd535f160a6702
Original thread:    https://lkml.kernel.org/lkml/000000000000785e9d0589ec359a@google.com/T/#u

Unfortunately, this bug does not have a reproducer.

The original thread for this bug has received 1 reply, 56 days ago.

If you fix this bug, please add the following tag to the commit:
    Reported-by: syzbot+9742b1c6c7aedf18beda@syzkaller.appspotmail.com

If you send any email or patch for this bug, please consider replying to the
original thread.  For the git send-email command to use, or tips on how to reply
if the thread isn't in your mailbox, see the "Reply instructions" at
https://lkml.kernel.org/r/000000000000785e9d0589ec359a@google.com

Re: Reminder: 2 open syzbot bugs in "security/tomoyo" subsystem

[Tetsuo Handa]

On 2019/07/24 11:42, Eric Biggers wrote:
> --------------------------------------------------------------------------------
> Title:              KASAN: use-after-free Read in tomoyo_realpath_from_path
> Last occurred:      28 days ago
> Reported:           48 days ago
> Branches:           Mainline and others
> Dashboard link:     https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74
> Original thread:    https://lkml.kernel.org/lkml/0000000000004f43fa058a97f4d3@google.com/T/#u

A patch is available, but I can't find a chance to setup my git tree for sending
a pull request for the patch.

> --------------------------------------------------------------------------------
> Title:              KASAN: invalid-free in tomoyo_realpath_from_path
> Last occurred:      57 days ago
> Reported:           56 days ago
> Branches:           net-next
> Dashboard link:     https://syzkaller.appspot.com/bug?id=e9e5a1d41c3fb5d0f79aeea0e4cd535f160a6702
> Original thread:    https://lkml.kernel.org/lkml/000000000000785e9d0589ec359a@google.com/T/#u

This cannot be a TOMOYO's bug. We are waiting for a reproducer but
no crash occurred since then. Maybe it is time to close as invalid.

Re: Reminder: 2 open syzbot bugs in "security/tomoyo" subsystem

[Eric Biggers]

On Wed, Jul 24, 2019 at 12:18:47PM +0900, Tetsuo Handa wrote:
> > --------------------------------------------------------------------------------
> > Title:              KASAN: invalid-free in tomoyo_realpath_from_path
> > Last occurred:      57 days ago
> > Reported:           56 days ago
> > Branches:           net-next
> > Dashboard link:     https://syzkaller.appspot.com/bug?id=e9e5a1d41c3fb5d0f79aeea0e4cd535f160a6702
> > Original thread:    https://lkml.kernel.org/lkml/000000000000785e9d0589ec359a@google.com/T/#u
> 
> This cannot be a TOMOYO's bug. We are waiting for a reproducer but
> no crash occurred since then. Maybe it is time to close as invalid.

Maybe.  Did you check for stack buffer overflows in the functions that
tomoyo_realpath_from_path() calls?  Perhaps something is corrupting the 'buf'
variable in the parent's stack frame.

- Eric

Re: Reminder: 2 open syzbot bugs in "security/tomoyo" subsystem

[Tetsuo Handa]

On 2019/07/24 13:34, Eric Biggers wrote:
> On Wed, Jul 24, 2019 at 12:18:47PM +0900, Tetsuo Handa wrote:
>>> --------------------------------------------------------------------------------
>>> Title:              KASAN: invalid-free in tomoyo_realpath_from_path
>>> Last occurred:      57 days ago
>>> Reported:           56 days ago
>>> Branches:           net-next
>>> Dashboard link:     https://syzkaller.appspot.com/bug?id=e9e5a1d41c3fb5d0f79aeea0e4cd535f160a6702
>>> Original thread:    https://lkml.kernel.org/lkml/000000000000785e9d0589ec359a@google.com/T/#u
>>
>> This cannot be a TOMOYO's bug. We are waiting for a reproducer but
>> no crash occurred since then. Maybe it is time to close as invalid.
> 
> Maybe.  Did you check for stack buffer overflows in the functions that
> tomoyo_realpath_from_path() calls?  Perhaps something is corrupting the 'buf'
> variable in the parent's stack frame.
> 

What do you mean? If this crash were a stack buffer overflow, this crash
should have already occurred again.

Since the "buf" variable is a local variable, it cannot be shared between
two threads. Since "buf" is assigned as

  buf = kmalloc(buf_len, GFP_NOFS);

and nobody else is reassigning "buf",

  kfree(buf);

can't become an invalid free.

Re: Reminder: 2 open syzbot bugs in "security/tomoyo" subsystem

[Eric Biggers]

On Wed, Jul 24, 2019 at 01:54:40PM +0900, Tetsuo Handa wrote:
> On 2019/07/24 13:34, Eric Biggers wrote:
> > On Wed, Jul 24, 2019 at 12:18:47PM +0900, Tetsuo Handa wrote:
> >>> --------------------------------------------------------------------------------
> >>> Title:              KASAN: invalid-free in tomoyo_realpath_from_path
> >>> Last occurred:      57 days ago
> >>> Reported:           56 days ago
> >>> Branches:           net-next
> >>> Dashboard link:     https://syzkaller.appspot.com/bug?id=e9e5a1d41c3fb5d0f79aeea0e4cd535f160a6702
> >>> Original thread:    https://lkml.kernel.org/lkml/000000000000785e9d0589ec359a@google.com/T/#u
> >>
> >> This cannot be a TOMOYO's bug. We are waiting for a reproducer but
> >> no crash occurred since then. Maybe it is time to close as invalid.
> > 
> > Maybe.  Did you check for stack buffer overflows in the functions that
> > tomoyo_realpath_from_path() calls?  Perhaps something is corrupting the 'buf'
> > variable in the parent's stack frame.
> > 
> 
> What do you mean? If this crash were a stack buffer overflow, this crash
> should have already occurred again.
> 

Well not necessarily, it could be very rare.

That being said, it was only seen on net-next and only once; so it could have
been caused by some broken patch elsewhere in the kernel that was only present
for a short time.

So if you aren't going to do anything else with this, please just go ahead and
invalidate it.

> Since the "buf" variable is a local variable, it cannot be shared between
> two threads. Since "buf" is assigned as
> 
>   buf = kmalloc(buf_len, GFP_NOFS);
> 
> and nobody else is reassigning "buf",
> 
>   kfree(buf);
> 
> can't become an invalid free.
> 

- Eric

Reminder: 2 open syzbot bugs in "security/tomoyo" subsystem

[Eric Biggers]

[This email was generated by a script.  Let me know if you have any suggestions
to make it better, or if you want it re-generated with the latest status.]

Of the currently open syzbot reports against the upstream kernel, I've manually
marked 2 of them as possibly being bugs in the "security/tomoyo" subsystem. 
I've listed these reports below, sorted by an algorithm that tries to list first
the reports most likely to be still valid, important, and actionable.

If you believe a bug is no longer valid, please close the syzbot report by
sending a '#syz fix', '#syz dup', or '#syz invalid' command in reply to the
original thread, as explained at https://goo.gl/tpsmEJ#status

If you believe I misattributed a bug to the "security/tomoyo" subsystem, please
let me know, and if possible forward the report to the correct people or mailing
list.

Here are the bugs:

--------------------------------------------------------------------------------
Title:              KASAN: use-after-free Read in tomoyo_realpath_from_path
Last occurred:      6 days ago
Reported:           26 days ago
Branches:           Mainline and others
Dashboard link:     https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74
Original thread:    https://lkml.kernel.org/lkml/0000000000004f43fa058a97f4d3@google.com/T/#u

This bug has a syzkaller reproducer only.

The original thread for this bug has received 7 replies; the last was 9 days
ago.

If you fix this bug, please add the following tag to the commit:
    Reported-by: syzbot+0341f6a4d729d4e0acf1@syzkaller.appspotmail.com

If you send any email or patch for this bug, please reply to the original
thread, which had activity only 9 days ago.  For the git send-email command to
use, or tips on how to reply if the thread isn't in your mailbox, see the "Reply
instructions" at https://lkml.kernel.org/r/0000000000004f43fa058a97f4d3@google.com

--------------------------------------------------------------------------------
Title:              KASAN: invalid-free in tomoyo_realpath_from_path
Last occurred:      35 days ago
Reported:           34 days ago
Branches:           net-next
Dashboard link:     https://syzkaller.appspot.com/bug?id=e9e5a1d41c3fb5d0f79aeea0e4cd535f160a6702
Original thread:    https://lkml.kernel.org/lkml/000000000000785e9d0589ec359a@google.com/T/#u

Unfortunately, this bug does not have a reproducer.

The original thread for this bug has received 1 reply, 34 days ago.

If you fix this bug, please add the following tag to the commit:
    Reported-by: syzbot+9742b1c6c7aedf18beda@syzkaller.appspotmail.com

If you send any email or patch for this bug, please consider replying to the
original thread.  For the git send-email command to use, or tips on how to reply
if the thread isn't in your mailbox, see the "Reply instructions" at
https://lkml.kernel.org/r/000000000000785e9d0589ec359a@google.com