From: Carlos O'Donell <carlos@redhat.com>
To: Siddhesh Poyarekar <siddhesh@gotplt.org>,
Arjun Shankar <arjun@redhat.com>,
libc-alpha@sourceware.org
Subject: Re: [PATCH v4] socket: Check lengths before advancing pointer in CMSG_NXTHDR
Date: Fri, 29 Jul 2022 12:43:01 -0400 [thread overview]
Message-ID: <4631785f-d873-bdf7-c315-b673f15c55ff@redhat.com> (raw)
In-Reply-To: <a2352da1-09ee-00f8-ac57-45c3a5a1f30f@gotplt.org>
On 7/29/22 12:40, Siddhesh Poyarekar wrote:
> On 2022-07-29 09:26, Arjun Shankar wrote:
>> The inline and library functions that the CMSG_NXTHDR macro may expand
>> to increment the pointer to the header before checking the stride of
>> the increment against available space. Since C only allows incrementing
>> pointers to one past the end of an array, the increment must be done
>> after a length check. This commit fixes that and includes a regression
>> test for CMSG_FIRSTHDR and CMSG_NXTHDR.
>>
>> The Linux, Hurd, and generic headers are all changed.
>>
>> Tested on Linux on armv7hl, i686, x86_64, aarch64, ppc64le, and s390x.
>>
>> [BZ #28846]
>> ---
>> v3: https://sourceware.org/pipermail/libc-alpha/2022-July/140854.html
>>
>> Notes on v4:
>>
>> * Addressed review comments from Siddhesh:
>>
>> 1. (sizeof (struct cmsghdr) + __CMSG_PADDING (cmsg_len)):
>> defined as size_needed.
>>
>> 2.
>>> OK, but I wonder if there's utility in making the padding a generic
>>> macro, e.g.
>>
>>> #define ALIGN_PADDING(n, a) ((a - (n & (a - 1))) & (a - 1))
>>
>> This sounds useful, and actually it would be great to move *all* of the
>> duplicate code between these versions into a separate file and include it
>> in these variants. I'll try to do a follow-up with this soon. I'm going to
>> note it down in my TODO.
>>
>> 3.
>>> __msg_control_ptr doesn't really need the __ since it's a local variable.
>>
>> I thought so too. But Florian pointed out that it would interfere with
>> things like users #define'ing msg_control_ptr before including socket.h.
>> ---
>> bits/socket.h | 40 ++++++++++--
>> socket/Makefile | 1 +
>> socket/tst-cmsghdr-skeleton.c | 92 +++++++++++++++++++++++++++
>> socket/tst-cmsghdr.c | 56 ++++++++++++++++
>> sysdeps/mach/hurd/bits/socket.h | 40 ++++++++++--
>> sysdeps/unix/sysv/linux/bits/socket.h | 40 ++++++++++--
>> sysdeps/unix/sysv/linux/cmsg_nxthdr.c | 36 ++++++++---
>> 7 files changed, 276 insertions(+), 29 deletions(-)
>> create mode 100644 socket/tst-cmsghdr-skeleton.c
>> create mode 100644 socket/tst-cmsghdr.c
>
> LGTM.
>
> Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Just a reminder that the branch is frozen for glibc 2.36 release.
This is good for 2.37 when it opens.
--
Cheers,
Carlos.
prev parent reply other threads:[~2022-07-29 16:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-29 13:26 Arjun Shankar
2022-07-29 16:40 ` Siddhesh Poyarekar
2022-07-29 16:43 ` Carlos O'Donell [this message]
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