linux-kernel - [PATCH 4/5] kprobes: Do not expose probe addresses to non-CAP

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Message-Id: <20200702232638.2946421-5-keescook@chromium.org>
Date:   Thu,  2 Jul 2020 16:26:37 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Dominik Czarnota <dominik.czarnota@...ilofbits.com>
Cc:     Kees Cook <keescook@...omium.org>, stable@...r.kernel.org,
        Jessica Yu <jeyu@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        KP Singh <kpsingh@...omium.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Will Deacon <will@...nel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Matteo Croce <mcroce@...hat.com>,
        Edward Cree <ecree@...arflare.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Alexander Lobakin <alobakin@...nk.ru>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Ingo Molnar <mingo@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] 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: stable@...r.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@...omium.org>
---
 kernel/kprobes.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d4de217e4a91..2e97febeef77 100644
--- 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
-- 
2.25.1