linux-kernel - [PATCH 3.16 392/410] tracing: probeevent: Fix to support minus offset from symbol

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Message-ID: <lsq.1528380321.503328813@decadent.org.uk>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        "Masami Hiramatsu" <mhiramat@...nel.org>,
        "Ingo Molnar" <mingo@...hat.com>,
        "Ravi Bangoria" <ravi.bangoria@...ux.vnet.ibm.com>,
        "Arnaldo Carvalho de Melo" <acme@...nel.org>,
        "Tom Zanussi" <tom.zanussi@...ux.intel.com>,
        "Namhyung Kim" <namhyung@...nel.org>
Subject: [PATCH 3.16 392/410] tracing: probeevent: Fix to support minus
 offset from symbol

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Masami Hiramatsu <mhiramat@...nel.org>

commit c5d343b6b7badd1f5fe0873eff2e8d63a193e732 upstream.

In Documentation/trace/kprobetrace.txt, it says

 @SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)

However, the parser doesn't parse minus offset correctly, since
commit 2fba0c8867af ("tracing/kprobes: Fix probe offset to be
unsigned") drops minus ("-") offset support for kprobe probe
address usage.

This fixes the traceprobe_split_symbol_offset() to parse minus
offset again with checking the offset range, and add a minus
offset check in kprobe probe address usage.

Link: http://lkml.kernel.org/r/152129028983.31874.13419301530285775521.stgit@devbox

Cc: Ingo Molnar <mingo@...hat.com>
Cc: Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Fixes: 2fba0c8867af ("tracing/kprobes: Fix probe offset to be unsigned")
Acked-by: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/trace/trace_kprobe.c | 4 ++--
 kernel/trace/trace_probe.c  | 8 +++-----
 kernel/trace/trace_probe.h  | 2 +-
 3 files changed, 6 insertions(+), 8 deletions(-)

--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -611,7 +611,7 @@ static int create_trace_kprobe(int argc,
 	bool is_return = false, is_delete = false;
 	char *symbol = NULL, *event = NULL, *group = NULL;
 	char *arg;
-	unsigned long offset = 0;
+	long offset = 0;
 	void *addr = NULL;
 	char buf[MAX_EVENT_NAME_LEN];
 
@@ -684,7 +684,7 @@ static int create_trace_kprobe(int argc,
 		symbol = argv[1];
 		/* TODO: support .init module functions */
 		ret = traceprobe_split_symbol_offset(symbol, &offset);
-		if (ret) {
+		if (ret || offset < 0 || offset > UINT_MAX) {
 			pr_info("Failed to parse either an address or a symbol.\n");
 			return ret;
 		}
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -291,7 +291,7 @@ static fetch_func_t get_fetch_size_funct
 }
 
 /* Split symbol and offset. */
-int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
+int traceprobe_split_symbol_offset(char *symbol, long *offset)
 {
 	char *tmp;
 	int ret;
@@ -299,13 +299,11 @@ int traceprobe_split_symbol_offset(char
 	if (!offset)
 		return -EINVAL;
 
-	tmp = strchr(symbol, '+');
+	tmp = strpbrk(symbol, "+-");
 	if (tmp) {
-		/* skip sign because kstrtoul doesn't accept '+' */
-		ret = kstrtoul(tmp + 1, 0, offset);
+		ret = kstrtol(tmp, 0, offset);
 		if (ret)
 			return ret;
-
 		*tmp = '\0';
 	} else
 		*offset = 0;
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -341,7 +341,7 @@ extern int traceprobe_conflict_field_nam
 extern void traceprobe_update_arg(struct probe_arg *arg);
 extern void traceprobe_free_probe_arg(struct probe_arg *arg);
 
-extern int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset);
+extern int traceprobe_split_symbol_offset(char *symbol, long *offset);
 
 extern ssize_t traceprobe_probes_write(struct file *file,
 		const char __user *buffer, size_t count, loff_t *ppos,