Messages in this thread | | | Date | Fri, 5 Jun 2015 23:40:03 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 09/10] uprobes: Change prepare_uretprobe() to (try to) flush the dead frames |
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On 05/04, Oleg Nesterov wrote: > > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -1522,6 +1522,16 @@ static unsigned long get_trampoline_vaddr(void) > return trampoline_vaddr; > } > > +static void cleanup_return_instances(struct uprobe_task *utask, struct pt_regs *regs) > +{ > + struct return_instance *ri = utask->return_instances; > + while (ri && !arch_uretprobe_is_alive(&ri->auret, regs)) { > + ri = free_ret_instance(ri); > + utask->depth--; > + } > + utask->return_instances = ri; > +} > + > static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs) > { > struct return_instance *ri; > @@ -1576,6 +1586,9 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs) > ri->orig_ret_vaddr = orig_ret_vaddr; > ri->chained = chained; > > + if (utask->depth) /* drop the entries invalidated by longjmp() */ > + cleanup_return_instances(utask, regs); > +
Self nack ;)
Note that that prepare_uretprobe() does
if (orig_ret_vaddr == trampoline_vaddr) { if (!utask->return_instances) { /* * This situation is not possible. Likely we have an * attack from user-space. */ pr_warn("uprobe: unable to set uretprobe pid/tgid=%d/%d\n", current->pid, current->tgid); goto fail;
_before_ we do cleanup_return_instances().
This is actually fine in a sense that ->return_instances == NULL after cleanup_return_instances() is not possible if chained, there should be another _alive() frame. But malicious user can obviously fool the kernel.
Easy to fix. But after discussion with Srikar and Pratyush (thanks!) I decided to update 6-10.
Oleg.
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