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    Subject[PATCH v3 3/7] kprobes: validate the symbol name length
    Date
    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>
    ---
    include/linux/kprobes.h | 1 +
    kernel/kprobes.c | 24 ++++++++++++++++++++++++
    kernel/trace/trace_kprobe.c | 4 ++++
    3 files changed, 29 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..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;
    + }
    +
    + 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
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