linux-kernel - [PATCH 5/9] kprobes: Search non-suffixed symbol in blacklist

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Message-Id: <154708898461.6325.17046972809561067053.stgit@devbox>
Date:   Thu, 10 Jan 2019 11:56:24 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ingo Molnar <mingo@...hat.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>, peterz@...radead.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andrea Righi <righi.andrea@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>, stable@...r.kernel.org
Subject: [PATCH 5/9] kprobes: Search non-suffixed symbol in blacklist

Newer gcc can generate some different instances of a function
with suffixed symbols if the function is optimized and only
has a part of that. (e.g. .constprop, .part etc.)

In this case, it is not enough to check the entry of kprobe
blacklist because it only records non-suffixed symbol address.

To fix this issue, search non-suffixed symbol in blacklist if
given address is within a symbol which has a suffix.

Note that this can cause false positive cases if a kprobe-safe
function is optimized to suffixed instance and has same name
symbol which is blacklisted.
But I would like to chose a fail-safe design for this issue.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 kernel/kprobes.c |   21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index e8c76164f541..faa519f07aad 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1396,7 +1396,7 @@ bool __weak arch_within_kprobe_blacklist(unsigned long addr)
 	       addr < (unsigned long)__kprobes_text_end;
 }
 
-bool within_kprobe_blacklist(unsigned long addr)
+static bool __within_kprobe_blacklist(unsigned long addr)
 {
 	struct kprobe_blacklist_entry *ent;
 
@@ -1410,7 +1410,26 @@ bool within_kprobe_blacklist(unsigned long addr)
 		if (addr >= ent->start_addr && addr < ent->end_addr)
 			return true;
 	}
+	return false;
+}
 
+bool within_kprobe_blacklist(unsigned long addr)
+{
+	char symname[KSYM_NAME_LEN], *p;
+
+	if (__within_kprobe_blacklist(addr))
+		return true;
+
+	/* Check if the address is on a suffixed-symbol */
+	if (!lookup_symbol_name(addr, symname)) {
+		p = strchr(symname, '.');
+		if (!p)
+			return false;
+		*p = '\0';
+		addr = (unsigned long)kprobe_lookup_name(symname, 0);
+		if (addr)
+			return __within_kprobe_blacklist(addr);
+	}
 	return false;
 }