From: "Eric W. Biederman" <ebiederm@xmission.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Ariadne Conill <ariadne@dereferenced.org>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Kees Cook <keescook@chromium.org>,
Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v2] fs/exec: require argv[0] presence in do_execveat_common()
Date: Wed, 26 Jan 2022 10:57:29 -0600 [thread overview]
Message-ID: <877damwi2u.fsf@email.froward.int.ebiederm.org> (raw)
In-Reply-To: <YfFh6O2JS6MybamT@casper.infradead.org> (Matthew Wilcox's message of "Wed, 26 Jan 2022 14:59:52 +0000")
Matthew Wilcox <willy@infradead.org> writes:
> On Wed, Jan 26, 2022 at 11:44:47AM +0000, Ariadne Conill wrote:
>> Interestingly, Michael Kerrisk opened an issue about this in 2008[1],
>> but there was no consensus to support fixing this issue then.
>> Hopefully now that CVE-2021-4034 shows practical exploitative use
>> of this bug in a shellcode, we can reconsider.
>>
>> [0]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
>> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=8408
>
> Having now read 8408 ... if ABI change is a concern (and I really doubt
> it is), we could treat calling execve() with a NULL argv as if the
> caller had passed an array of length 1 with the first element set to
> NULL. Just like we reopen fds 0,1,2 for suid execs if they were
> closed.
Where do we reopen fds 0,1,2 for suid execs? I feel silly but I looked
through the code fs/exec.c quickly and I could not see it.
I am attracted to the notion of converting an empty argv array passed
to the kernel into something we can safely pass to userspace.
I think it would need to be having the first entry point to "" instead
of the first entry being NULL. That would maintain the invariant that you
can always dereference a pointer in the argv array.
Eric
next prev parent reply other threads:[~2022-01-26 16:58 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-26 11:44 [PATCH v2] fs/exec: require argv[0] presence in do_execveat_common() Ariadne Conill
2022-01-26 14:40 ` Matthew Wilcox
2022-01-26 17:41 ` Ariadne Conill
2022-01-26 14:59 ` Matthew Wilcox
2022-01-26 16:40 ` Kees Cook
2022-01-26 16:57 ` Eric W. Biederman [this message]
2022-01-26 17:32 ` Ariadne Conill
2022-01-26 18:03 ` Matthew Wilcox
2022-01-26 18:38 ` Ariadne Conill
2022-01-26 20:09 ` Kees Cook
2022-01-26 20:23 ` Ariadne Conill
2022-01-26 20:56 ` Kees Cook
2022-01-26 21:13 ` Ariadne Conill
2022-01-26 21:25 ` Kees Cook
2022-01-26 21:30 ` Ariadne Conill
2022-01-26 22:49 ` Kees Cook
2022-01-26 23:07 ` Ariadne Conill
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