Hi,
On Mon, 9 Nov 2020 22:55:38 -0500 Sasha Levin sashal@kernel.org wrote:
From: "Steven Rostedt (VMware)" rostedt@goodmis.org
[ 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@kernel.org
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@infradead.org Acked-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org
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