Messages in this thread | | | Date | Thu, 20 Apr 2017 07:19:28 +0000 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH v3 3/7] kprobes: validate the symbol name length |
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Excerpts from Michael Ellerman's message of April 20, 2017 11:38: > "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> writes: > >> 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) >> +{ >> + size_t sym_len; >> + char *s; >> + >> + s = strchr(name, ':'); >> + if (s) { >> + sym_len = strnlen(s+1, 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) >> + return false; >> + } > > I think this is probably more elaborate than it needs to be. > > Why not just check the string is <= (MODULE_NAME_LEN + KSYM_NAME_LEN) ?
Yes, that would be sufficient for now.
It's probably just me being paranoid, but I felt it's good to have stricter checks for user-provided strings, to guard against future changes to how we process this.
- Naveen
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