From: Masami Hiramatsu <mhiramat@kernel.org>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Ingo Molnar <mingo@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH v3 3/7] kprobes: validate the symbol name length
Date: Tue, 25 Apr 2017 12:18:31 +0900 [thread overview]
Message-ID: <20170425121831.2868474af583522facd73981@kernel.org> (raw)
In-Reply-To: <1492962128.c0nhtlqdo4.astroid@naverao1-tp.none>
On Sun, 23 Apr 2017 15:44:32 +0000
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
> >> >> +bool is_valid_kprobe_symbol_name(const char *name)
> >> >
> >> > This just check the length of symbol_name buffer, and can contain
> >> > some invalid chars.
> >>
> >> Yes, I kept the function name generic incase we would like to do more
> >> validation in future, plus it's shorter than
> >> is_valid_kprobe_symbol_name_len() ;-)
> >
> > OK, if this is enough general, we'd better define this in
> > kernel/kallsyms.c or in kallsyms.h. Of course the function
> > should be called is_valid_symbol_name(). :-)
>
> I actually think this should be done in kprobes itself. The primary
> intent is to perform such validation right when we first obtain the
> input from the user. In this case, however, kallsyms_lookup_name() is
> also an exported symbol, so I do think some validation there would be
> good to have as well.
IMHO, it is natural that kallsyms will know what is valid symbols.
Providing validation function by kprobes means kprobes also knows
that, and I concerns that may lead a double standard.
Thanks,
> >> >> +{
> >> >> + size_t sym_len;
> >> >> + char *s;
> >> >> +
> >> >> + s = strchr(name, ':');
> >>
> >> Hmm.. this should be strnchr(). I re-factored the code that moved the
> >> strnlen() above this below. I'll fix this.
> >>
> >> >> + if (s) {
> >> >> + sym_len = strnlen(s+1, KSYM_NAME_LEN);
> >> >
> >> > If you use strnlen() here, you just need to ensure sym_len < KSYM_NAME_LEN.
> >>
> >> Hmm.. not sure I follow. Are you saying the check for sym_len <= 0 is
> >> not needed?
> >
> > You can check sym_len != 0, but anyway, here we concern about
> > "longer" string (for performance reason), we can focus on
> > such case.
> > (BTW, could you also check the name != NULL at first?)
> >
> > So, what I think it can be;
> >
> > if (strnlen(s+1, KSYM_NAME_LEN) == KSYM_NAME_LEN ||
> > (size_t)(s - name) >= MODULE_NAME_LEN)
> > return false;
>
> Sure, thanks. I clearly need to refactor this code better!
>
> - Naveen
>
>
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2017-04-25 3:18 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 12:50 [PATCH v3 0/7] powerpc: a few kprobe fixes and refactoring Naveen N. Rao
2017-04-19 12:51 ` [PATCH v3 1/7] kprobes: convert kprobe_lookup_name() to a function Naveen N. Rao
2017-04-24 22:47 ` [v3,1/7] " Michael Ellerman
2017-04-19 12:51 ` [PATCH v3 2/7] powerpc: kprobes: fix handling of function offsets on ABIv2 Naveen N. Rao
2017-04-24 22:47 ` [v3,2/7] " Michael Ellerman
2017-04-19 12:51 ` [PATCH v3 3/7] kprobes: validate the symbol name length Naveen N. Rao
2017-04-19 14:37 ` Masami Hiramatsu
2017-04-19 16:38 ` Naveen N. Rao
2017-04-21 13:42 ` Masami Hiramatsu
2017-04-23 15:44 ` Naveen N. Rao
2017-04-25 3:18 ` Masami Hiramatsu [this message]
2017-04-20 6:08 ` Michael Ellerman
2017-04-20 7:19 ` Naveen N. Rao
2017-04-21 12:32 ` [PATCH v4 3/7] kprobes: validate the symbol name provided during probe registration Naveen N. Rao
2017-04-21 13:11 ` Paul Clarke
2017-04-21 13:25 ` Naveen N. Rao
2017-04-21 13:54 ` Masami Hiramatsu
2017-04-22 5:55 ` Michael Ellerman
2017-04-23 17:41 ` Naveen N. Rao
2017-04-21 12:33 ` [PATCH v4 4/7] powerpc/kprobes: Use safer string functions in kprobe_lookup_name() Naveen N. Rao
2017-04-21 13:33 ` Paul Clarke
2017-04-21 13:36 ` Paul Clarke
2017-04-21 13:52 ` Paul Clarke
2017-04-23 17:09 ` Naveen N. Rao
2017-04-19 12:51 ` [PATCH v3 4/7] powerpc: kprobes: use " Naveen N. Rao
2017-04-21 15:06 ` David Laight
2017-04-19 12:51 ` [PATCH v3 5/7] powerpc: kprobes: factor out code to emulate instruction into a helper Naveen N. Rao
2017-04-19 14:40 ` Masami Hiramatsu
2017-04-24 22:47 ` [v3, " Michael Ellerman
2017-04-19 12:51 ` [PATCH v3 6/7] powerpc: kprobes: emulate instructions on kprobe handler re-entry Naveen N. Rao
2017-04-19 14:43 ` Masami Hiramatsu
2017-04-19 16:42 ` Naveen N. Rao
2017-04-20 6:11 ` Michael Ellerman
2017-04-21 13:48 ` Masami Hiramatsu
2017-04-24 22:47 ` [v3, " Michael Ellerman
2017-04-19 12:51 ` [PATCH v3 7/7] powerpc: kprobes: remove duplicate saving of msr Naveen N. Rao
2017-04-19 14:43 ` Masami Hiramatsu
2017-04-23 11:53 ` [v3,7/7] " Michael Ellerman
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