linux-kernel - Re: Possible Memory Leak in KCOV Linux 4.15-rc1

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Message-ID: <CACT4Y+ZcbKWkS5Zd6uAynL=PKF7KbTBWrxnkkPXb0spV0-EDsg@mail.gmail.com>
Date:   Sat, 20 Jan 2018 13:38:52 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Shankara Pailoor <sp3485@...umbia.edu>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: Possible Memory Leak in KCOV Linux 4.15-rc1

On Fri, Jan 19, 2018 at 8:29 PM, Shankara Pailoor <sp3485@...umbia.edu> wrote:
> Hi Dmitry,
>
> I added support for kcov in strace and I have been tracing a fairly
> large program but after a little while, I notice that when I mmap a
> new cover buffer, the call fails with ENOMEM. After killing the
> program, I try and rerun and I notice that there is nearly no memory
> on the system. When I do a kmemleak scan I get the following reports:
>
> I believe the problem occurs when I try and setup the kcov buffer
> again after an exec. Instead of reusing the old file descriptor I open
> kcov again within that process. In that case, I don't know what
> happens to the old kcov struct.
>
> I don't see a maintainers list for kcov so I decided to email you
> directly. Let me know what more information I can provide.


Hi Shankara,

Looks bad. Can you provide a reproducer?
We extensively use kcov with syzkaller, but have not observed such
leaks. Also I don't see anything obvious in the code.

Thanks