Re: [PATCH v2] drivers/base: Fix length checks in create_syslog_header()/dev_vprintk_emit()

From: Ben Hutchings
Date: Fri Jul 11 2014 - 13:21:17 EST

On Wed, 2014-07-09 at 16:57 -0700, Greg Kroah-Hartman wrote:
> On Sun, Jun 08, 2014 at 11:51:43PM +0100, Ben Hutchings wrote:
> > snprintf() returns the number of bytes that could have been written
> > (excluding the null), not the actual number of bytes written. Given a
> > long enough subsystem or device name, these functions will advance
> > beyond the end of the on-stack buffer in dev_vprintk_exit(), resulting
> > in an information leak or stack corruption. I don't know whether such
> > a long name is currently possible.
> >
> > In case snprintf() returns a value >= the buffer size, do not add
> > structured logging information. Also WARN if this happens, so we can
> > fix the driver or increase the buffer size.
> >
> > Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> > ---
> > v2: use dev_WARN() not dev_WARN_ON()
> This patch breaks the build in a huge way:
> drivers/base/core.c: In function âcreate_syslog_headerâ:
> drivers/base/core.c:2049:16: error: expected â)â before numeric constant
> dev_WARN(dev, 1, "device/subsystem name too long");
> ^
> is the start of it, it goes on for a page or so after that :(

Sorry about that, I must not have committed the working version before
mailing it. If you delete the '1, ' it should work. If you've already
deleted the patch, I'll check and send the working version.


Ben Hutchings
To err is human; to really foul things up requires a computer.

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