Hi, On Mon, 9 Nov 2020 22:55:38 -0500 Sasha Levin <sashal@xxxxxxxxxx> wrote: > From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx> > > [ Upstream commit 645f224e7ba2f4200bf163153d384ceb0de5462e ] > > Since the kprobe handlers have protection that prohibits other handlers from > executing in other contexts (like if an NMI comes in while processing a > kprobe, and executes the same kprobe, it will get fail with a "busy" > return). Lockdep is unaware of this protection. Use lockdep's nesting api to > differentiate between locks taken in INT3 context and other context to > suppress the false warnings. > > Link: https://lore.kernel.org/r/20201102160234.fa0ae70915ad9e2b21c08b85@xxxxxxxxxx > This fixes a lockdep false positive warning comes from commit e03b4a084ea6 ("kprobes: Remove NMI context check"). Does anyone report that happen on the stable kernel? If not, you do not need this patch for stable kernels. Thank you, > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > kernel/kprobes.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 2161f519d4812..2ce9053de6ae4 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1204,7 +1204,13 @@ __acquires(hlist_lock) > > *head = &kretprobe_inst_table[hash]; > hlist_lock = kretprobe_table_lock_ptr(hash); > - raw_spin_lock_irqsave(hlist_lock, *flags); > + /* > + * Nested is a workaround that will soon not be needed. > + * There's other protections that make sure the same lock > + * is not taken on the same CPU that lockdep is unaware of. > + * Differentiate when it is taken in NMI context. > + */ > + raw_spin_lock_irqsave_nested(hlist_lock, *flags, !!in_nmi()); > } > NOKPROBE_SYMBOL(kretprobe_hash_lock); > > @@ -1213,7 +1219,13 @@ static void kretprobe_table_lock(unsigned long hash, > __acquires(hlist_lock) > { > raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash); > - raw_spin_lock_irqsave(hlist_lock, *flags); > + /* > + * Nested is a workaround that will soon not be needed. > + * There's other protections that make sure the same lock > + * is not taken on the same CPU that lockdep is unaware of. > + * Differentiate when it is taken in NMI context. > + */ > + raw_spin_lock_irqsave_nested(hlist_lock, *flags, !!in_nmi()); > } > NOKPROBE_SYMBOL(kretprobe_table_lock); > > @@ -1884,7 +1896,12 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) > > /* TODO: consider to only swap the RA after the last pre_handler fired */ > hash = hash_ptr(current, KPROBE_HASH_BITS); > - raw_spin_lock_irqsave(&rp->lock, flags); > + /* > + * Nested is a workaround that will soon not be needed. > + * There's other protections that make sure the same lock > + * is not taken on the same CPU that lockdep is unaware of. > + */ > + raw_spin_lock_irqsave_nested(&rp->lock, flags, 1); > if (!hlist_empty(&rp->free_instances)) { > ri = hlist_entry(rp->free_instances.first, > struct kretprobe_instance, hlist); > @@ -1895,7 +1912,7 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) > ri->task = current; > > if (rp->entry_handler && rp->entry_handler(ri, regs)) { > - raw_spin_lock_irqsave(&rp->lock, flags); > + raw_spin_lock_irqsave_nested(&rp->lock, flags, 1); > hlist_add_head(&ri->hlist, &rp->free_instances); > raw_spin_unlock_irqrestore(&rp->lock, flags); > return 0; > -- > 2.27.0 > -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
