Hi,
1-st issue: unprotected iteration over the IRQ action list in name_unique()
the racing sequences:
[ 1 ] request_irq() -> setup_irq() -> register_handler_proc() ->
name_unique() -> iterate over the action list (*)
setup_irq() releases a desc->lock before calling register_handler_proc().
[ 2 ] free_irq() -> delete some element while (*) is still in progress -> bum!
something like this should make it safe :
--- kernel/irq/proc-old.c 2007-03-14 16:34:52.828981000 +0100
+++ kernel/irq/proc.c 2007-03-14 16:59:47.236950000 +0100
@@ -66,11 +66,18 @@ static int name_unique(unsigned int irq,
{
struct irq_desc *desc = irq_desc + irq;
struct irqaction *action;
+ unsigned long flags;
+
+ spin_lock_irqsave(&desc->lock, flags);
for (action = desc->action ; action; action = action->next)
if ((action != new_action) && action->name &&
- !strcmp(new_action->name, action->name))
+ !strcmp(new_action->name, action->name)) {
+ spin_unlock_irqrestore(&desc->lock, flags);
return 0;
+ }
+
+ spin_unlock_irqrestore(&desc->lock, flags);
return 1;
}
2-nd issue: now it's about register_irq_proc() which is also called
by setup_irq().
register_irq_proc() is called for all descriptors for which
(irq_desc[irq].chip == &no_irq_chip) != 0 (*)
at startup time from init_irq_proc().
Let's suppose (*) is not true for some desc at startup and changes at
some point later.
If so, register_irq_proc() takes effect being called from setup_irq().
Now let's suppose request_irq() is called on 2 cpus for the same
interrupt line and both end up in (%) below
[ request_irq() -> setup_irq() -> register_irq_proc() ]
void register_irq_proc(unsigned int irq)
{
char name [MAX_NAMELEN];
if (!root_irq_dir ||
(irq_desc[irq].chip == &no_irq_chip) ||
irq_desc[irq].dir)
return;
(%) <=== both are here
memset(name, 0, MAX_NAMELEN);
sprintf(name, "%d", irq);
/* create /proc/irq/1234 */
irq_desc[irq].dir = proc_mkdir(name, root_irq_dir);
...
Both will try to initialize "irq_desc[irq].dir" and "smp_affinity"
entry... Not bum, but a possible leak indeed.
TIA,
--
Best regards,
Dmitry Adamushko
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