korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-11-25 05:04:09 +08:00
Code Issues Packages Projects Releases Wiki Activity

x86/kprobes: Avoid kretprobe recursion bug

Browse Source 
Avoid kretprobe recursion loop bg by setting a dummy
kprobes to current_kprobe per-CPU variable.

This bug has been introduced with the asm-coded trampoline
code, since previously it used another kprobe for hooking
the function return placeholder (which only has a nop) and
trampoline handler was called from that kprobe.

This revives the old lost kprobe again.

With this fix, we don't see deadlock anymore.

And you can see that all inner-called kretprobe are skipped.

  event_1                                  235               0
  event_2                                19375           19612

The 1st column is recorded count and the 2nd is missed count.
Above shows (event_1 rec) + (event_2 rec) ~= (event_2 missed)
(some difference are here because the counter is racy)

Reported-by: Andrea Righi <righi.andrea@gmail.com>
Tested-by: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: c9becf58d9 ("[PATCH] kretprobe: kretprobe-booster")
Link: http://lkml.kernel.org/r/155094064889.6137.972160690963039.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Masami Hiramatsu 2019-02-24 01:50:49 +09:00 committed by Ingo Molnar
parent fabe38ab6b
commit b191fa96ea
1 changed files with 20 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
arch/x86/kernel/kprobes/core.c
View File

@ -749,11 +749,16 @@ asm(
NOKPROBE_SYMBOL(kretprobe_trampoline);
STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
static struct kprobe kretprobe_kprobe = {
.addr = (void *)kretprobe_trampoline,
};
/*
* Called from kretprobe_trampoline
*/
static __used void *trampoline_handler(struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb;
struct kretprobe_instance *ri = NULL;
struct hlist_head *head, empty_rp;
struct hlist_node *tmp;
@ -763,6 +768,17 @@ static __used void *trampoline_handler(struct pt_regs *regs)
void *frame_pointer;
bool skipped = false;
preempt_disable();
/*
* Set a dummy kprobe for avoiding kretprobe recursion.
* Since kretprobe never run in kprobe handler, kprobe must not
* be running at this point.
*/
kcb = get_kprobe_ctlblk();
__this_cpu_write(current_kprobe, &kretprobe_kprobe);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
INIT_HLIST_HEAD(&empty_rp);
kretprobe_hash_lock(current, &head, &flags);
/* fixup registers */
@ -838,10 +854,9 @@ static __used void *trampoline_handler(struct pt_regs *regs)
orig_ret_address = (unsigned long)ri->ret_addr;
if (ri->rp && ri->rp->handler) {
__this_cpu_write(current_kprobe, &ri->rp->kp);
get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
ri->ret_addr = correct_ret_addr;
ri->rp->handler(ri, regs);
__this_cpu_write(current_kprobe, NULL);
__this_cpu_write(current_kprobe, &kretprobe_kprobe);
}
recycle_rp_inst(ri, &empty_rp);
@ -857,6 +872,9 @@ static __used void *trampoline_handler(struct pt_regs *regs)
kretprobe_hash_unlock(current, &flags);
__this_cpu_write(current_kprobe, NULL);
preempt_enable();
hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
hlist_del(&ri->hlist);
kfree(ri);