On Tue, Jul 07, 2015 at 03:23:06AM +0200, Oleg Nesterov wrote:
> Change prepare_uretprobe() to flush the !arch_uretprobe_is_alive()
> return_instance's. This is not needed correctness-wise, but can help
> to avoid the failure caused by MAX_URETPROBE_DEPTH.
>
> Note: in this case arch_uretprobe_is_alive() can be false positive,
> the stack can grow after longjmp(). Unfortunately, the kernel can't
> 100% solve this problem, but see the next patch.
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
Acked-by: Anton Arapov <ara...@gmail.com>
> ---
> kernel/events/uprobes.c | 13 +++++++++++++
> 1 files changed, 13 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 93d939c..7e61c8c 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1511,6 +1511,16 @@ 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, 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;
> @@ -1541,6 +1551,9 @@ static void prepare_uretprobe(struct uprobe *uprobe,
> struct pt_regs *regs)
> if (orig_ret_vaddr == -1)
> goto fail;
>
> + /* drop the entries invalidated by longjmp() */
> + cleanup_return_instances(utask, regs);
> +
> /*
> * We don't want to keep trampoline address in stack, rather keep the
> * original return address of first caller thru all the consequent
> --
> 1.5.5.1
>
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