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RE: [PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a function

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Excerpts from David Laight's message of April 18, 2017 18:22:
> From: Naveen N. Rao
>> Sent: 12 April 2017 11:58
> ...
>> +kprobe_opcode_t *kprobe_lookup_name(const char *name)
>> +{
> ...
>> +	char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
>> +	const char *modsym;
>> +	bool dot_appended = false;
>> +	if ((modsym = strchr(name, ':')) != NULL) {
>> +		modsym++;
>> +		if (*modsym != '\0' && *modsym != '.') {
>> +			/* Convert to <module:.symbol> */
>> +			strncpy(dot_name, name, modsym - name);
>> +			dot_name[modsym - name] = '.';
>> +			dot_name[modsym - name + 1] = '\0';
>> +			strncat(dot_name, modsym,
>> +				sizeof(dot_name) - (modsym - name) - 2);
>> +			dot_appended = true;
> 
> If the ':' is 'a way down' name[] then although the strncpy() won't
> overrun dot_name[] the rest of the code can.

Nice catch, thanks David!
We need to be validating the length of 'name'. I'll put out a patch for 
that.

As an aside, I'm not sure I follow what you mean when you say that the 
strncpy() won't overrun dot_name[]. If we have a name[] longer than 
sizeof(dot_name) with the ':' after that, the strncpy() can also overrun 
dot_name[].


- Naveen

> 
> The strncat() call is particularly borked.
> 
> 	David
> 
> 

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[PATCH v2 0/5] powerpc: a few kprobe fixes and refactoring "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-12 13:00 +0200
  [PATCH v2 2/5] powerpc: kprobes: fix handling of function offsets on ABIv2 "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-12 13:10 +0200
    Re: [PATCH v2 2/5] powerpc: kprobes: fix handling of function  offsets on ABIv2 Masami Hiramatsu <mhiramat@kernel.org> - 2017-04-13 06:30 +0200
  [PATCH v2 3/5] powerpc: introduce a new helper to obtain function entry points "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-12 13:10 +0200
    Re: [PATCH v2 3/5] powerpc: introduce a new helper to obtain  function entry points Masami Hiramatsu <mhiramat@kernel.org> - 2017-04-13 06:40 +0200
      Re: [PATCH v2 3/5] powerpc: introduce a new helper to obtain  function entry points "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-13 08:00 +0200
  [PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a function "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-12 13:10 +0200
    Re: [PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a  function Masami Hiramatsu <mhiramat@kernel.org> - 2017-04-13 05:10 +0200
    RE: [PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a  function David Laight <David.Laight@ACULAB.COM> - 2017-04-18 15:00 +0200
      RE: [PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a  function "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-19 10:10 +0200
        RE: [PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a  function David Laight <David.Laight@ACULAB.COM> - 2017-04-19 10:50 +0200
          Re: [PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a  function "'Naveen N. Rao'" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-19 13:10 +0200
  [PATCH v2 4/5] powerpc: kprobes: factor out code to emulate instruction into a helper "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-12 13:10 +0200
    Re: [PATCH v2 4/5] powerpc: kprobes: factor out code to emulate  instruction into a helper Masami Hiramatsu <mhiramat@kernel.org> - 2017-04-13 06:40 +0200
      Re: [PATCH v2 4/5] powerpc: kprobes: factor out code to emulate  instruction into a helper "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-13 08:00 +0200
      Re: [PATCH v2 4/5] powerpc: kprobes: factor out code to emulate  instruction into a helper "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-13 11:00 +0200
  [PATCH v2 5/5] powerpc: kprobes: emulate instructions on kprobe handler re-entry "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-12 13:10 +0200
    Re: [PATCH v2 5/5] powerpc: kprobes: emulate instructions on kprobe  handler re-entry Masami Hiramatsu <mhiramat@kernel.org> - 2017-04-13 06:40 +0200
      Re: [PATCH v2 5/5] powerpc: kprobes: emulate instructions on kprobe  handler re-entry "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-13 08:00 +0200
  Re: [PATCH v2 0/5] powerpc: a few kprobe fixes and refactoring Masami Hiramatsu <mhiramat@kernel.org> - 2017-04-13 05:10 +0200
    Re: [PATCH v2 0/5] powerpc: a few kprobe fixes and refactoring "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-04-13 08:00 +0200

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