Messages in this thread Patch in this message | | | From | "Naveen N. Rao" <> | Subject | [PATCH v4 3/7] kprobes: validate the symbol name provided during probe registration | Date | Fri, 21 Apr 2017 18:02:33 +0530 |
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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.
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> --- Masami, Michael, Here's a simplified version that should hopefully be fine. I have simplified the logic to keep the code compact and simple.
- Naveen
include/linux/kprobes.h | 1 + kernel/kprobes.c | 30 ++++++++++++++++++++++++++++++ kernel/trace/trace_kprobe.c | 4 ++++ 3 files changed, 35 insertions(+)
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h index 1f82a3db00b1..4ee10fef5135 100644 --- a/include/linux/kprobes.h +++ b/include/linux/kprobes.h @@ -405,6 +405,7 @@ int disable_kprobe(struct kprobe *kp); int enable_kprobe(struct kprobe *kp); void dump_kprobe(struct kprobe *kp); +bool is_valid_kprobe_symbol_name(const char *name); #else /* !CONFIG_KPROBES: */ diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 6a128f3a7ed1..ff9b1ac72a38 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1383,6 +1383,34 @@ bool within_kprobe_blacklist(unsigned long addr) } /* + * We mainly want to ensure that the provided string is of a reasonable length + * and is of the form [<mod_name>:]<sym_name>, so that this is safe to process + * further. + * We don't worry about invalid characters as those will just prevent + * matching existing kallsyms. + */ +bool is_valid_kprobe_symbol_name(const char *name) +{ + size_t sym_len; + const char *s; + + s = strnchr(name, ':', MODULE_NAME_LEN + KSYM_NAME_LEN + 1); + if (s) { + sym_len = (size_t)(s - name); + if (sym_len <= 0 || sym_len >= MODULE_NAME_LEN) + return false; + s++; + } else + s = name; + + sym_len = strnlen(s, KSYM_NAME_LEN); + if (sym_len <= 0 || sym_len >= KSYM_NAME_LEN) + 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. * This returns encoded errors if it fails to look up symbol or invalid @@ -1397,6 +1425,8 @@ 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
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