Re: [PATCH] kprobes: Fix NULL pointer dereference in unregister_kretprobes()

[JP Kobryn]

On 8/5/2026 9:12 AM, Luigi Rizzo wrote:

In unregister_kretprobes(), rps[i]->rph can be NULL e.g. when called
after kretprobe failed registration. Under !CONFIG_KRETPROBE_ON_RETHOOK,
the unconditional access to rps[i]->rph->rp, causes a kernel panic due
to NULL pointer dereference.

Add a NULL check for rps[i]->rph before invoking rcu_assign_pointer().

Fixes: d839a656d0f3 ("kprobes: consistent rcu api usage for kretprobe holder")

The bug was not introduced in this commit. It goes further back to:

d741bf41d7c7 ("kprobes: Remove kretprobe hash")

Signed-off-by: Luigi Rizzo <lri...@google.com>
---
  kernel/kprobes.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index bfc89083daa93..5dd4786c455de 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2359,7 +2359,8 @@ void unregister_kretprobes(struct kretprobe **rps, int 
num)
  #ifdef CONFIG_KRETPROBE_ON_RETHOOK
                rethook_free(rps[i]->rh);
  #else
-               rcu_assign_pointer(rps[i]->rph->rp, NULL);
+               if (rps[i]->rph)
+                       rcu_assign_pointer(rps[i]->rph->rp, NULL);
  #endif
        }