Messages in this thread | | | Date | Tue, 24 Jan 2023 09:00:26 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH] kprobes: Fix to handle forcibly unoptimized kprobes on freeing_list |
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On Mon, 23 Jan 2023 13:39:31 -0500 Steven Rostedt <rostedt@goodmis.org> wrote:
> 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>
Thanks for review! I'll fix typos and put on probes/urgent. Also, Cc: stable@vger.kernel.org
Thank you,
> > -- Steve
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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