From: David Gibson <david@gibson.dropbear.id.au>
To: passt-dev@passt.top
Subject: Re: [PATCH 21/28] cppcheck: Suppress NULL pointer warning in tcp_sock_consume()
Date: Thu, 29 Sep 2022 11:07:41 +1000 [thread overview]
Message-ID: <YzTv3UngFH/Lynbo@yekko> (raw)
In-Reply-To: <20220928225837.190a0fed@elisabeth>
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On Wed, Sep 28, 2022 at 10:58:37PM +0200, Stefano Brivio wrote:
> On Wed, 28 Sep 2022 14:33:32 +1000
> David Gibson <david(a)gibson.dropbear.id.au> wrote:
>
> > Recent versions of cppcheck give a warning due to the NULL buffer passed
> > to recv() in tcp_sock_consume(). Since this apparently works, I assume
> > it's actually valid,
>
> Yes, given that we use MSG_TRUNC to discard socket buffers, I thought
> it's cleaner to avoid supplying a data buffer altogether.
>
> POSIX doesn't specify MSG_TRUNC, and whether the buffer can be NULL
> isn't specified in Linux documentation, but it works reliably (the
> kernel won't even look at it).
Ah, interesting. I've update the comment and commit message with this
detail.
> This was actually the first step of a long-overdue plan: if you observe
> this through perf(1), you'll see some overhead in the kernel, which
> looks a bit more than a reasonable expectation for pure syscall
> overhead.
>
> So, I planned to check if we can simplify the kernel path if no buffer
> is passed. I'll track this somewhere next week.
>
> Even the day we add a vhost-user back-end, this overhead is still going
> to be there, as that wouldn't change anything host-side.
>
> > but cppcheck doesn't know that recv() can take a NULL
> > buffer. So, use a suppression to get rid of the error.
>
> valgrind didn't know either, by the way -- see the corresponding
> suppression in test/valgrind.supp.
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2022-09-29 1:07 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-28 4:33 [PATCH 00/28] Fixes for static checkers David Gibson
2022-09-28 4:33 ` [PATCH 01/28] Clean up parsing of port ranges David Gibson
2022-09-28 20:57 ` Stefano Brivio
2022-09-29 1:04 ` David Gibson
2022-09-28 4:33 ` [PATCH 02/28] clang-tidy: Suppress warning about unchecked error in logfn macro David Gibson
2022-09-28 4:33 ` [PATCH 03/28] clang-tidy: Fix spurious null pointer warning in pasta_start_ns() David Gibson
2022-09-28 4:33 ` [PATCH 04/28] clang-tidy: Remove duplicate #include from icmp.c David Gibson
2022-09-28 4:33 ` [PATCH 05/28] Catch failures when installing signal handlers David Gibson
2022-09-28 4:33 ` [PATCH 06/28] Pack DHCPv6 "on wire" structures David Gibson
2022-09-28 4:33 ` [PATCH 07/28] Clean up parsing in conf_runas() David Gibson
2022-09-28 20:57 ` Stefano Brivio
2022-09-29 1:44 ` David Gibson
2022-09-28 4:33 ` [PATCH 08/28] cppcheck: Reduce scope of some variables David Gibson
2022-09-28 4:33 ` [PATCH 09/28] Don't shadow 'i' in conf_ports() David Gibson
2022-09-28 4:33 ` [PATCH 10/28] Don't shadow global function names David Gibson
2022-09-28 4:33 ` [PATCH 11/28] Stricter checking for nsholder.c David Gibson
2022-09-28 4:33 ` [PATCH 12/28] cppcheck: Work around false positive NULL pointer dereference error David Gibson
2022-09-28 4:33 ` [PATCH 13/28] cppcheck: Use inline suppression for ffsl() David Gibson
2022-09-28 4:33 ` [PATCH 14/28] cppcheck: Use inline suppressions for qrap.c David Gibson
2022-09-28 4:33 ` [PATCH 15/28] cppcheck: Use inline suppression for strtok() in conf.c David Gibson
2022-09-28 4:33 ` [PATCH 16/28] Avoid ugly 'end' members in netlink structures David Gibson
2022-09-28 4:33 ` [PATCH 17/28] cppcheck: Broaden suppression for unused struct members David Gibson
2022-09-28 4:33 ` [PATCH 18/28] cppcheck: Remove localtime suppression for pcap.c David Gibson
2022-09-28 4:33 ` [PATCH 19/28] qrap: Handle case of PATH environment variable being unset David Gibson
2022-09-28 4:33 ` [PATCH 20/28] cppcheck: Suppress same-value-in-ternary branches warning David Gibson
2022-09-28 20:58 ` Stefano Brivio
2022-09-29 1:00 ` David Gibson
2022-09-28 4:33 ` [PATCH 21/28] cppcheck: Suppress NULL pointer warning in tcp_sock_consume() David Gibson
2022-09-28 20:58 ` Stefano Brivio
2022-09-29 1:07 ` David Gibson [this message]
2022-09-28 4:33 ` [PATCH 22/28] Regenerate seccomp.h if seccomp.sh changes David Gibson
2022-09-28 4:33 ` [PATCH 23/28] cppcheck: Avoid errors due to zeroes in bitwise ORs David Gibson
2022-09-28 4:33 ` [PATCH 24/28] cppcheck: Remove unused knownConditionTrueFalse suppression David Gibson
2022-09-28 20:58 ` Stefano Brivio
2022-09-29 1:24 ` David Gibson
2022-09-28 4:33 ` [PATCH 25/28] cppcheck: Remove unused objectIndex suppressions David Gibson
2022-09-28 20:58 ` Stefano Brivio
2022-09-29 1:12 ` David Gibson
2022-09-28 4:33 ` [PATCH 26/28] cppcheck: Remove unused va_list_usedBeforeStarted suppression David Gibson
2022-09-28 4:33 ` [PATCH 27/28] Mark unused functions for cppcheck David Gibson
2022-09-28 4:33 ` [PATCH 28/28] cppcheck: Remove unused unmatchedSuppression suppressions David Gibson
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