linux-kernel - [PATCH 4.16 80/81] kprobes: Fix random address output of blacklist file

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Date:   Fri, 27 Apr 2018 15:59:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        David S Miller <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>, acme@...nel.org,
        Thomas Richter <tmricht@...ux.ibm.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 4.16 80/81] kprobes: Fix random address output of blacklist file

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Richter <tmricht@...ux.ibm.com>

commit bcbd385b61bbdef3491d662203ac2e8186e5be59 upstream.

File /sys/kernel/debug/kprobes/blacklist displays random addresses:

[root@...60046 linux]# cat /sys/kernel/debug/kprobes/blacklist
0x0000000047149a90-0x00000000bfcb099a	print_type_x8
....

This breaks 'perf probe' which uses the blacklist file to prohibit
probes on certain functions by checking the address range.

Fix this by printing the correct (unhashed) address.

The file mode is read all but this is not an issue as the file
hierarchy points out:
 # ls -ld /sys/ /sys/kernel/ /sys/kernel/debug/ /sys/kernel/debug/kprobes/
	/sys/kernel/debug/kprobes/blacklist
dr-xr-xr-x 12 root root 0 Apr 19 07:56 /sys/
drwxr-xr-x  8 root root 0 Apr 19 07:56 /sys/kernel/
drwx------ 16 root root 0 Apr 19 06:56 /sys/kernel/debug/
drwxr-xr-x  2 root root 0 Apr 19 06:56 /sys/kernel/debug/kprobes/
-r--r--r--  1 root root 0 Apr 19 06:56 /sys/kernel/debug/kprobes/blacklist

Everything in and below /sys/kernel/debug is rwx to root only,
no group or others have access.

Background:
Directory /sys/kernel/debug/kprobes is created by debugfs_create_dir()
which sets the mode bits to rwxr-xr-x. Maybe change that to use the
parent's directory mode bits instead?

Link: http://lkml.kernel.org/r/20180419105556.86664-1-tmricht@linux.ibm.com

Fixes: ad67b74d2469 ("printk: hash addresses printed with %p")
Cc: stable@...r.kernel.org
Cc: <stable@...r.kernel.org> # v4.15+
Cc: Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
Cc: David S Miller <davem@...emloft.net>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: acme@...nel.org

Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/kprobes.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2428,7 +2428,7 @@ static int kprobe_blacklist_seq_show(str
 	struct kprobe_blacklist_entry *ent =
 		list_entry(v, struct kprobe_blacklist_entry, list);
 
-	seq_printf(m, "0x%p-0x%p\t%ps\n", (void *)ent->start_addr,
+	seq_printf(m, "0x%px-0x%px\t%ps\n", (void *)ent->start_addr,
 		   (void *)ent->end_addr, (void *)ent->start_addr);
 	return 0;
 }