Messages in this thread Patch in this message | | | Date | Wed, 24 Oct 2007 19:26:04 +0200 | From | Adrian Bunk <> | Subject | Re: [2.6 patch] acpi/ec.c: fix use-after-free |
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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@kernel.org> > > > > --- > > --- 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
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