Messages in this thread | | | Date | Mon, 23 Jan 2023 13:39:31 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] kprobes: Fix to handle forcibly unoptimized kprobes on freeing_list |
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On Mon, 23 Jan 2023 22:24:05 +0900 "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
> From: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > Sinec forcibly unoptimized kprobes will be put on the freeing_list directly
"Since"
> in the unoptimize_kprobe(), do_unoptimize_kprobes() must continue to check > the freeing_list even if unoptimizing_list is empty. > > This bug can be happen if a kprobe is put in an instruction which is in the
"This bug can happen if"
> middle of the jump-replaced instruction sequence of an optprobe, *and* the > optprobe is recently unregistered and queued on unoptimizing_list. > In this case, the optprobe will be unoptimized forcibly (means immediately) > and put it into the freeing_list, expecting the optprobe will be handled in > do_unoptimize_kprobe(). > But if there is no other optprobes on the unoptimizing_list, current code > returns from the do_unoptimize_kprobe() soon and do not handle the optprobe
"and does not handle'
> which is on the freeing_list, and it will hit the WARN_ON_ONCE() in the > do_free_cleaned_kprobes(), because it is not handled in the latter loop of > the do_unoptimize_kprobe(). > > To solve this issue, do not return from do_unoptimize_kprobes() immediately > even if unoptimizing_list is empty. > > Moreover, this change affects another case. kill_optimized_kprobes() expects > kprobe_optimizer() will just free the optprobe on freeing_list. > So I changed it to just do list_move() to freeing_list if optprobes are on > unoptimizing list. And the do_unoptimize_kprobe() will skip > arch_disarm_kprobe() if the probe on freeing_list has gone flag. > > Link: https://lore.kernel.org/all/Y8URdIfVr3pq2X8w@xpf.sh.intel.com/ > > Fixes: e4add247789e ("kprobes: Fix optimize_kprobe()/unoptimize_kprobe() cancellation logic") > Reported-by: Pengfei Xu <pengfei.xu@intel.com> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > --- > kernel/kprobes.c | 23 ++++++++++------------- > 1 file changed, 10 insertions(+), 13 deletions(-) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 1c18ecf9f98b..73b150fad936 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -555,17 +555,15 @@ static void do_unoptimize_kprobes(void) > /* See comment in do_optimize_kprobes() */ > lockdep_assert_cpus_held(); > > - /* Unoptimization must be done anytime */ > - if (list_empty(&unoptimizing_list)) > - return; > + if (!list_empty(&unoptimizing_list)) > + arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list); > > - arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list); > - /* Loop on 'freeing_list' for disarming */ > + /* Loop on 'freeing_list' for disarming and removing from kprobe hash list */ > list_for_each_entry_safe(op, tmp, &freeing_list, list) { > /* Switching from detour code to origin */ > op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED; > - /* Disarm probes if marked disabled */ > - if (kprobe_disabled(&op->kp)) > + /* Disarm probes if marked disabled and not gone */ > + if (kprobe_disabled(&op->kp) && !kprobe_gone(&op->kp)) > arch_disarm_kprobe(&op->kp); > if (kprobe_unused(&op->kp)) { > /* > @@ -797,14 +795,13 @@ static void kill_optimized_kprobe(struct kprobe *p) > op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED; > > if (kprobe_unused(p)) { > - /* Enqueue if it is unused */ > - list_add(&op->list, &freeing_list); > /* > - * Remove unused probes from the hash list. After waiting > - * for synchronization, this probe is reclaimed. > - * (reclaiming is done by do_free_cleaned_kprobes().) > + * Unused kprobe is on unoptimizing or freeing list. We move it > + * to freeing_list and let the kprobe_optimizer() removes it from
"remove it"
> + * the kprobe hash list and frees it.
"and free it."
> */ > - hlist_del_rcu(&op->kp.hlist); > + if (optprobe_queued_unopt(op)) > + list_move(&op->list, &freeing_list); > } > > /* Don't touch the code, because it is already freed. */
Other than the spelling issues,
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
-- Steve
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