Adrian Bunk wrote:
> 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.
Yes, found it minute before :(
Acked, thanks.
>
>
>> 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
>
-
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