Re: [PATCH bpf] x86/kprobes: Fix KRETPROBES when CONFIG_KRETPROBE_ON_RETHOOK is set

[Daniel Borkmann <daniel@iogearbox.net>]

On 4/26/22 10:50 AM, Masami Hiramatsu wrote:
> On Mon, 25 Apr 2022 16:42:12 +0200
> Daniel Borkmann <daniel@iogearbox.net> wrote:
>> On 4/22/22 6:40 PM, Adam Zabrocki wrote:
>>> [PATCH bpf] x86/kprobes: Fix KRETPROBES when CONFIG_KRETPROBE_ON_RETHOOK is set
>>>
>>> The recent kernel change "kprobes: Use rethook for kretprobe if possible",
>>> introduced a potential NULL pointer dereference bug in the KRETPROBE
>>> mechanism. The official Kprobes documentation defines that "Any or all
>>> handlers can be NULL". Unfortunately, there is a missing return handler
>>> verification to fulfill these requirements and can result in a NULL pointer
>>> dereference bug.
>>>
>>> This patch adds such verification in kretprobe_rethook_handler() function.
>>>
>>> Fixes: 73f9b911faa7 ("kprobes: Use rethook for kretprobe if possible")
>>> Signed-off-by: Adam Zabrocki <pi3@pi3.com.pl>
>>> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
>>
>> I don't mind if this fix gets routed via bpf tree if all parties are okay with
>> it (Masami? Steven?). Just noting that there is currently no specific dependency
>> in bpf tree for it, but if it's easier to route this way, happy to take it.
> 
> Yeah, I and Steve talked about it and he suggested this to be merged
> via BPF tree since the original commit came from the BPF tree.

Okay, I just applied it to bpf tree then.

Thanks everyone,
Daniel