[PATCH] SEGV in libsysfs/dlist.c

[PATCH] SEGV in libsysfs/dlist.c

[Hannes Reinecke]

[-- Attachment #1: Type: text/plain, Size: 346 bytes --]

Hi all, Greg,

libsysfs/dlist.c: _dlist_mark_move()

is missing checks for empty lists and may (and indeed, does) crash when 
called with empty dlists.

Please apply.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke			hare@suse.de
SuSE Linux AG				S390 & zSeries
Maxfeldstraße 5				+49 911 74053 688
90409 Nürnberg				http://www.suse.de

[-- Attachment #2: libsysfs-dlist.patch --]
[-- Type: text/plain, Size: 503 bytes --]

===== dlist.c 1.3 vs edited =====
--- 1.3/libsysfs/dlist.c	Wed Mar 10 18:12:14 2004
+++ edited/dlist.c	Thu Mar 18 13:11:00 2004
@@ -74,14 +74,14 @@
 {
   if(direction)
     {
-      if( list->marker->next!=NULL)
+      if( list->marker && list->marker->next!=NULL)
 	list->marker=list->marker->next;
       else
 	return(NULL);
     }
   else
     {
-      if( list->marker->prev!=NULL)
+      if( list->marker && list->marker->prev!=NULL)
 	list->marker=list->marker->prev;
       else
 	return(NULL);

Re: [PATCH] SEGV in libsysfs/dlist.c

[Greg KH]

On Thu, Mar 18, 2004 at 01:15:35PM +0100, Hannes Reinecke wrote:
> Hi all, Greg,
> 
> libsysfs/dlist.c: _dlist_mark_move()
> 
> is missing checks for empty lists and may (and indeed, does) crash when 
> called with empty dlists.

What code causes this to happen?  udev?  If so, where?

thanks,

greg k-h


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Re: [PATCH] SEGV in libsysfs/dlist.c

[Ananth N Mavinakayanahalli]

On Wed, Mar 24, 2004 at 03:15:06PM -0800, Greg KH wrote:
> On Thu, Mar 18, 2004 at 01:15:35PM +0100, Hannes Reinecke wrote:
> > Hi all, Greg,
> > 
> > libsysfs/dlist.c: _dlist_mark_move()
> > 
> > is missing checks for empty lists and may (and indeed, does) crash when 
> > called with empty dlists.
> 
> What code causes this to happen?  udev?  If so, where?
> 
When a "get" function is called for obtaining a list, (of say, attirbutes)
it returns a NULL either because it was not able to retrieve the data from 
sysfs (in which case the errno is set appropriately) or if the list is 
NULL (because there are no elements exposed thru' sysfs), in which case 
the errno is "0". If the list is not checked to be NULL, there
is a possibility of a de-referencing a NULL pointer. 

Libsysfs takes care of this situation internally. With Dr. Hannes' patch,
we do not have to bother of segfaulting even if a NULL is passed.


Thanks,
Ananth



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Re: [PATCH] SEGV in libsysfs/dlist.c

[Greg KH]

On Thu, Mar 18, 2004 at 01:15:35PM +0100, Hannes Reinecke wrote:
> Hi all, Greg,
> 
> libsysfs/dlist.c: _dlist_mark_move()
> 
> is missing checks for empty lists and may (and indeed, does) crash when 
> called with empty dlists.
> 
> Please apply.

Applied, thanks.

greg k-h


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