On Wed, Oct 24, 2007 at 09:15:18PM +0400, Alexey Starikovskiy wrote:
> Adrian,
>
> commit 30c08574da0ead1a47797ce028218ce5b2de61c7 can not introduce use-after-free.
>
> Please check...
Commit 30c08574da0ead1a47797ce028218ce5b2de61c7 did:
<-- snip -->
list_for_each_entry(handler, &ec->list, node) {
if (query_bit == handler->query_bit) {
list_del(&handler->node);
kfree(handler);
- break;
}
}
<-- snip -->
If you look at the definition of list_for_each_entry() in
include/linux/list.h:
<-- snip -->
#define list_for_each_entry(pos, head, member) \
for (pos = list_entry((head)->next, typeof(*pos), member); \
prefetch(pos->member.next), &pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*pos), member))
^^^^^^^^^^^^^^^^
<-- snip -->
Without the "break", "handler" is being dereferenced after it was freed.
> Regards,
> Alex.
> Adrian Bunk wrote:
> > This patch fixes a use-after-free introduced by
> > commit 30c08574da0ead1a47797ce028218ce5b2de61c7.
> >
> > Spotted by the Coverity checker.
> >
> > Signed-off-by: Adrian Bunk <bunk@xxxxxxxxxx>
> >
> > ---
> > --- linux-2.6/drivers/acpi/ec.c.old 2007-10-23 19:39:47.000000000 +0200
> > +++ linux-2.6/drivers/acpi/ec.c 2007-10-23 19:34:55.000000000 +0200
> > @@ -434,11 +442,11 @@
> > EXPORT_SYMBOL_GPL(acpi_ec_add_query_handler);
> >
> > void acpi_ec_remove_query_handler(struct acpi_ec *ec, u8 query_bit)
> > {
> > - struct acpi_ec_query_handler *handler;
> > + struct acpi_ec_query_handler *handler, *tmp;
> > mutex_lock(&ec->lock);
> > - list_for_each_entry(handler, &ec->list, node) {
> > + list_for_each_entry_safe(handler, tmp, &ec->list, node) {
> > if (query_bit == handler->query_bit) {
> > list_del(&handler->node);
> > kfree(handler);
> > }
> >
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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