Messages in this thread | | | Date | Wed, 19 Apr 2017 23:37:50 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH v3 3/7] kprobes: validate the symbol name length |
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On Wed, 19 Apr 2017 18:21:02 +0530 "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
> When a kprobe is being registered, we use the symbol_name field to > lookup the address where the probe should be placed. Since this is a > user-provided field, let's ensure that the length of the string is > within expected limits.
Would we really need this? Of course it may filter out longer strings... anyway such name should be rejected by kallsyms.
[...] > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 6a128f3a7ed1..bb86681c8a10 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1382,6 +1382,28 @@ bool within_kprobe_blacklist(unsigned long addr) > return false; > } > > +bool is_valid_kprobe_symbol_name(const char *name)
This just check the length of symbol_name buffer, and can contain some invalid chars.
> +{ > + size_t sym_len; > + char *s; > + > + s = strchr(name, ':'); > + 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.
> + if (sym_len <= 0 || sym_len >= KSYM_NAME_LEN) > + return false; > + sym_len = (size_t)(s - name); > + if (sym_len <= 0 || sym_len >= MODULE_NAME_LEN) > + return false; > + } else { > + sym_len = strnlen(name, MODULE_NAME_LEN); > + if (sym_len <= 0 || sym_len >= MODULE_NAME_LEN)
Would you mean KSYM_NAME_LEN here?
> + return false; > + } > + > + return true; > +} > + > /* > * If we have a symbol_name argument, look it up and add the offset field > * to it. This way, we can specify a relative address to a symbol. > @@ -1397,6 +1419,8 @@ static kprobe_opcode_t *kprobe_addr(struct kprobe *p) > goto invalid; > > if (p->symbol_name) { > + if (!is_valid_kprobe_symbol_name(p->symbol_name)) > + return ERR_PTR(-EINVAL); > addr = kprobe_lookup_name(p->symbol_name, p->offset); > if (!addr) > return ERR_PTR(-ENOENT); > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 5f688cc724f0..bf73e5f31128 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -704,6 +704,10 @@ static int create_trace_kprobe(int argc, char **argv) > pr_info("Return probe must be used without offset.\n"); > return -EINVAL; > } > + if (!is_valid_kprobe_symbol_name(symbol)) { > + pr_info("Symbol name is too long.\n"); > + return -EINVAL; > + } > } > argc -= 2; argv += 2; > > -- > 2.12.1 >
Thanks,
-- Masami Hiramatsu <mhiramat@kernel.org>
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