2006-11-01 05:45:09

by Chris Wright

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

-stable review patch. If anyone has any objections, please let us know.
------------------

From: Jeff Garzik <[email protected]>

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 <[email protected]>
Cc: Karsten Keil <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
---
drivers/isdn/i4l/isdn_common.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

--- linux-2.6.18.1.orig/drivers/isdn/i4l/isdn_common.c
+++ linux-2.6.18.1/drivers/isdn/i4l/isdn_common.c
@@ -1134,9 +1134,12 @@ isdn_read(struct file *file, char __user
if (dev->drv[drvidx]->interface->readstat) {
if (count > dev->drv[drvidx]->stavail)
count = dev->drv[drvidx]->stavail;
- len = dev->drv[drvidx]->interface->
- readstat(buf, count, drvidx,
- isdn_minor2chan(minor));
+ len = dev->drv[drvidx]->interface->readstat(buf, count,
+ drvidx, isdn_minor2chan(minor));
+ if (len < 0) {
+ retval = len;
+ goto out;
+ }
} else {
len = 0;
}

--

2006-11-01 06:03:09

by Jeff Garzik

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

Chris Wright wrote:
> -stable review patch. If anyone has any objections, please let us know.
> ------------------
>
> From: Jeff Garzik <[email protected]>
>
> 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 <[email protected]>
> Cc: Karsten Keil <[email protected]>
> Cc: <[email protected]>
> Signed-off-by: Andrew Morton <[email protected]>
> Signed-off-by: Linus Torvalds <[email protected]>
> Signed-off-by: Chris Wright <[email protected]>

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

commit 7786ce192fc4917fb9b789dd823476ff8fd6cf66
Author: Jeff Garzik <[email protected]>
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.

2006-11-01 06:49:53

by Willy Tarreau

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

On Tue, Oct 31, 2006 at 09:34:29PM -0800, Chris Wright wrote:
> -stable review patch. If anyone has any objections, please let us know.
> ------------------
>
> From: Jeff Garzik <[email protected]>
>
> 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 <[email protected]>
> Cc: Karsten Keil <[email protected]>
> Cc: <[email protected]>
> Signed-off-by: Andrew Morton <[email protected]>
> Signed-off-by: Linus Torvalds <[email protected]>
> Signed-off-by: Chris Wright <[email protected]>
> ---
> drivers/isdn/i4l/isdn_common.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> --- linux-2.6.18.1.orig/drivers/isdn/i4l/isdn_common.c
> +++ linux-2.6.18.1/drivers/isdn/i4l/isdn_common.c
> @@ -1134,9 +1134,12 @@ isdn_read(struct file *file, char __user
> if (dev->drv[drvidx]->interface->readstat) {
> if (count > dev->drv[drvidx]->stavail)
> count = dev->drv[drvidx]->stavail;
> - len = dev->drv[drvidx]->interface->
> - readstat(buf, count, drvidx,
> - isdn_minor2chan(minor));
> + len = dev->drv[drvidx]->interface->readstat(buf, count,
> + drvidx, isdn_minor2chan(minor));
> + if (len < 0) {
> + retval = len;
> + goto out;
> + }
> } else {
> len = 0;
> }

Seems appropriate for 2.4 too. Jeff, Karsten, no objection ?

Willy

2006-11-01 09:18:28

by Karsten Keil

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

On Wed, Nov 01, 2006 at 08:49:22AM +0100, Willy Tarreau wrote:
> On Tue, Oct 31, 2006 at 09:34:29PM -0800, Chris Wright wrote:
> > -stable review patch. If anyone has any objections, please let us know.
> > ------------------
> >
> > From: Jeff Garzik <[email protected]>
> >
> > 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 <[email protected]>
> > Cc: Karsten Keil <[email protected]>
> > Cc: <[email protected]>
> > Signed-off-by: Andrew Morton <[email protected]>
> > Signed-off-by: Linus Torvalds <[email protected]>
> > Signed-off-by: Chris Wright <[email protected]>
> > ---
> > drivers/isdn/i4l/isdn_common.c | 9 ++++++---
> > 1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > --- linux-2.6.18.1.orig/drivers/isdn/i4l/isdn_common.c
> > +++ linux-2.6.18.1/drivers/isdn/i4l/isdn_common.c
> > @@ -1134,9 +1134,12 @@ isdn_read(struct file *file, char __user
> > if (dev->drv[drvidx]->interface->readstat) {
> > if (count > dev->drv[drvidx]->stavail)
> > count = dev->drv[drvidx]->stavail;
> > - len = dev->drv[drvidx]->interface->
> > - readstat(buf, count, drvidx,
> > - isdn_minor2chan(minor));
> > + len = dev->drv[drvidx]->interface->readstat(buf, count,
> > + drvidx, isdn_minor2chan(minor));
> > + if (len < 0) {
> > + retval = len;
> > + goto out;
> > + }
> > } else {
> > len = 0;
> > }
>
> Seems appropriate for 2.4 too. Jeff, Karsten, no objection ?
>

Yes, OK for me.

--
Karsten Keil
SuSE Labs
ISDN development