From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v2 3/3] intel_th: msu: Fix an off-by-one in attribute store
Date: Wed, 19 Dec 2018 20:21:51 +0100 [thread overview]
Message-ID: <20181219192151.GA4413@kroah.com> (raw)
In-Reply-To: <20181219151922.44839-4-alexander.shishkin@linux.intel.com>
On Wed, Dec 19, 2018 at 05:19:22PM +0200, Alexander Shishkin wrote:
> The 'nr_pages' attribute of the 'msc' subdevices parses a comma-separated
> list of window sizes, passed from userspace. However, there is a bug in
> the string parsing logic wherein it doesn't exclude the comma character
> from the range of characters as it consumes them. This leads to an
> out-of-bounds access given a sufficiently long list. For example:
>
> > # echo 8,8,8,8 > /sys/bus/intel_th/devices/0-msc0/nr_pages
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in memchr+0x1e/0x40
> > Read of size 1 at addr ffff8803ffcebcd1 by task sh/825
> >
> > CPU: 3 PID: 825 Comm: npktest.sh Tainted: G W 4.20.0-rc1+
> > Call Trace:
> > dump_stack+0x7c/0xc0
> > print_address_description+0x6c/0x23c
> > ? memchr+0x1e/0x40
> > kasan_report.cold.5+0x241/0x308
> > memchr+0x1e/0x40
> > nr_pages_store+0x203/0xd00 [intel_th_msu]
>
> Fix this by accounting for the comma character.
Ugh, this is one major reason sysfs files are "one value per file".
You should never have to "parse" a sysfs file for something like this.
It's a bit too late now, but please, never create such a sysfs file
again :(
greg k-h
prev parent reply other threads:[~2018-12-19 19:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-19 15:19 [PATCH v2 0/3] stm class/intel_th: Fixes for v4.20 Alexander Shishkin
2018-12-19 15:19 ` [PATCH v2 1/3] stm class: Fix a module refcount leak in policy creation error path Alexander Shishkin
2018-12-19 15:19 ` [PATCH v2 2/3] stm class: Add a reference to the SyS-T document Alexander Shishkin
2018-12-19 15:19 ` [PATCH v2 3/3] intel_th: msu: Fix an off-by-one in attribute store Alexander Shishkin
2018-12-19 19:21 ` Greg Kroah-Hartman [this message]
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