Re: [PATCH v4 4/7] powerpc/kprobes: Use safer string functions in kprobe_lookup_name()

From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Masami Hiramatsu <mhiramat@kernel.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	pc@us.ibm.com
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v4 4/7] powerpc/kprobes: Use safer string functions in kprobe_lookup_name()
Date: Sun, 23 Apr 2017 17:09:34 +0000	[thread overview]
Message-ID: <1492967265.w6y5305xmj.astroid@naverao1-tp.none> (raw)
In-Reply-To: <e3b3a444-fa98-5ed3-7dd7-a45d93db8b1f@us.ibm.com>

Excerpts from Paul Clarke's message of April 21, 2017 19:22:
> Sent too soon.  The suggestions don't guarantee null termination.  Refined, below. (Sorry for the noise.)

Yeah, the string operations here are a bit of a minefield...

> 
> On 04/21/2017 08:33 AM, Paul Clarke wrote:
>> On 04/21/2017 07:33 AM, Naveen N. Rao wrote:
>>> Convert usage of strchr()/strncpy()/strncat() to
>>> strnchr()/memcpy()/strlcat() for simpler and safer string manipulation.
> 
>>> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
>>> index 97b5eed1f76d..c73fb6e3b43f 100644
>>> --- a/arch/powerpc/kernel/kprobes.c
>>> +++ b/arch/powerpc/kernel/kprobes.c
>>> @@ -65,28 +65,27 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
>>>  	char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
>>>  	const char *modsym;
>>>  	bool dot_appended = false;
>>> -	if ((modsym = strchr(name, ':')) != NULL) {
>>> +	if ((modsym = strnchr(name, ':', MODULE_NAME_LEN)) != NULL) {

... as I just realized this is an epic FAIL! ;/

I will take my time to redo this.

- Naveen