Re: [PATCH 49/61] ISDN: fix drivers, by handling errors thrown by->readstat()

From: Jeff Garzik
Date: Wed Nov 01 2006 - 01:03:29 EST


Chris Wright wrote:
-stable review patch. If anyone has any objections, please let us know.
------------------

From: Jeff Garzik <jeff@xxxxxxxxxx>

This is a particularly ugly on-failure bug, possibly security, since the
lack of error handling here is covering up another class of bug: failure to
handle copy_to_user() return values.

The I4L API function ->readstat() returns an integer, and by looking at
several existing driver implementations, it is clear that a negative return
value was meant to indicate an error.

Given that several drivers already return a negative value indicating an
errno-style error, the current code would blindly accept that [negative]
value as a valid amount of bytes read. Obvious damage ensues.

Correcting ->readstat() handling to properly notice errors fixes the
existing code to work correctly on error, and enables future patches to
more easily indicate errors during operation.

Signed-off-by: Jeff Garzik <jeff@xxxxxxxxxx>
Cc: Karsten Keil <kkeil@xxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>

No objection, but I would think that you would also want the companion patch:

commit 7786ce192fc4917fb9b789dd823476ff8fd6cf66
Author: Jeff Garzik <jeff@xxxxxxxxxx>
Date: Tue Oct 17 00:10:40 2006 -0700

[PATCH] ISDN: check for userspace copy faults

Most of the ISDN ->readstat() implementations needed to check
copy_to_user() and put_user() return values.


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