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([2607:fb91:ac9:d9bf:2112:37bc:94a6:a6db]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-4599e24dfc5sm3683651fac.7.2026.08.05.13.25.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Aug 2026 13:25:27 -0700 (PDT) Message-ID: Date: Wed, 5 Aug 2026 13:25:35 -0700 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] kprobes: Fix NULL pointer dereference in unregister_kretprobes() To: Luigi Rizzo , Masami Hiramatsu , Naveen N Rao , Luigi Rizzo , "David S . Miller" Cc: linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260805161221.2428623-1-lrizzo@google.com> Content-Language: en-US From: JP Kobryn In-Reply-To: <20260805161221.2428623-1-lrizzo@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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 > --- > 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 > } >