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From: Johannes Berg <johannes@sipsolutions.net>
To: Julian Calaby <julian.calaby@gmail.com>,
	Chris Bainbridge <chris.bainbridge@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	aryabinin@virtuozzo.com, Julia Lawall <Julia.Lawall@lip6.fr>,
	kernel-janitors@vger.kernel.org, Joe Perches <joe@perches.com>
Subject: Re: [PATCH] net/mac80211/agg-rx.c: fix use of uninitialised values
Date: Thu, 28 Jan 2016 09:48:12 +0000	[thread overview]
Message-ID: <1453974492.2217.2.camel@sipsolutions.net> (raw)
In-Reply-To: <CAGRGNgXkvNfzM9Q1RO5kFwUWpFZbQ3mNQi3aVHcPTCw0A9fyFA@mail.gmail.com> (sfid-20160128_002736_648758_DED52DA5)

On Thu, 2016-01-28 at 10:27 +1100, Julian Calaby wrote:
> 
> This looks like a "big hammer" solution to this problem.

It is, in a way, but it also avoids future errors like it.

> I'd prefer to just set ->removed to false right after we set
> ->auto_seq as that should be faster, however I don't know if
> __ieee80211_start_rx_ba_session() is a fast path so I don't know if
> this is saving anything.

It's not supposed to be called frequently, no.

> On another note, this is an error that should be pretty easy to spot.
> Could any of the automated tools find cases where a struct containing
> a bool variable is kmalloc'd and returned without assigning all the
> bools?

I think you'd quickly drown in false positives, since "return" isn't
necessarily something that means it needs to have been fully
initialized.

johannes
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WARNING: multiple messages have this Message-ID (diff)
From: Johannes Berg <johannes@sipsolutions.net>
To: Julian Calaby <julian.calaby@gmail.com>,
	Chris Bainbridge <chris.bainbridge@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	aryabinin@virtuozzo.com, Julia Lawall <Julia.Lawall@lip6.fr>,
	kernel-janitors@vger.kernel.org, Joe Perches <joe@perches.com>
Subject: Re: [PATCH] net/mac80211/agg-rx.c: fix use of uninitialised values
Date: Thu, 28 Jan 2016 10:48:12 +0100	[thread overview]
Message-ID: <1453974492.2217.2.camel@sipsolutions.net> (raw)
In-Reply-To: <CAGRGNgXkvNfzM9Q1RO5kFwUWpFZbQ3mNQi3aVHcPTCw0A9fyFA@mail.gmail.com> (sfid-20160128_002736_648758_DED52DA5)

On Thu, 2016-01-28 at 10:27 +1100, Julian Calaby wrote:
> 
> This looks like a "big hammer" solution to this problem.

It is, in a way, but it also avoids future errors like it.

> I'd prefer to just set ->removed to false right after we set
> ->auto_seq as that should be faster, however I don't know if
> __ieee80211_start_rx_ba_session() is a fast path so I don't know if
> this is saving anything.

It's not supposed to be called frequently, no.

> On another note, this is an error that should be pretty easy to spot.
> Could any of the automated tools find cases where a struct containing
> a bool variable is kmalloc'd and returned without assigning all the
> bools?

I think you'd quickly drown in false positives, since "return" isn't
necessarily something that means it needs to have been fully
initialized.

johannes

  reply	other threads:[~2016-01-28  9:48 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-26 11:17 UBSAN: Undefined behaviour in net/mac80211/rx.c:924:18 Chris Bainbridge
2016-01-26 11:17 ` Chris Bainbridge
2016-01-27 15:46 ` [PATCH] net/mac80211/agg-rx.c: fix use of uninitialised values Chris Bainbridge
2016-01-27 23:27   ` Julian Calaby
2016-01-27 23:27     ` Julian Calaby
2016-01-28  9:48     ` Johannes Berg [this message]
2016-01-28  9:48       ` Johannes Berg
2016-01-28 10:11       ` Julian Calaby
2016-01-28 10:11         ` Julian Calaby
2016-01-28 10:24         ` Julia Lawall
2016-01-28 10:24           ` Julia Lawall
2016-01-28 12:30     ` Dan Carpenter
2016-01-28 12:30       ` Dan Carpenter
2016-01-28 12:35       ` Johannes Berg
2016-01-28 12:35         ` Johannes Berg
2016-01-28  9:47   ` Johannes Berg

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