kprobes: Do not expose probe addresses to non-CAP_SYSLOG

The kprobe show() functions were using "current"'s creds instead
of the file opener's creds for kallsyms visibility. Fix to use
seq_file->file->f_cred.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 81365a947de4 ("kprobes: Show address of kprobes if kallsyms does")
Fixes: ffb9bd68ebdb ("kprobes: Show blacklist addresses as same as kallsyms does")
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d4de217..2e97feb 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2448,7 +2448,7 @@ static void report_probe(struct seq_file *pi, struct kprobe *p,
        else
                kprobe_type = "k";
 
-       if (!kallsyms_show_value(current_cred()))
+       if (!kallsyms_show_value(pi->file->f_cred))
                addr = NULL;
 
        if (sym)
@@ -2540,7 +2540,7 @@ static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
         * If /proc/kallsyms is not showing kernel address, we won't
         * show them here either.
         */
-       if (!kallsyms_show_value(current_cred()))
+       if (!kallsyms_show_value(m->file->f_cred))
                seq_printf(m, "0x%px-0x%px\t%ps\n", NULL, NULL,
                           (void *)ent->start_addr);
        else