tracing: probeevent: Fix to support minus offset from symbol

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@redhat.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Fixes: 2fba0c8867af ("tracing/kprobes: Fix probe offset to be unsigned")
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

3 files changed, 6 insertions, 8 deletions

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 1fad24acd444..ae4147eaebd4 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -659,7 +659,7 @@ static int create_trace_kprobe(int argc, char **argv)
         char *symbol = NULL, *event = NULL, *group = NULL;
         int maxactive = 0;
         char *arg;
-        unsigned long offset = 0;
+        long offset = 0;
         void *addr = NULL;
         char buf[MAX_EVENT_NAME_LEN];
 
@@ -747,7 +747,7 @@ static int create_trace_kprobe(int argc, char **argv)
                 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;
                 }
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index d59357308677..daf54bda4dc8 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -320,7 +320,7 @@ static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
 }
 
 /* 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;
@@ -328,13 +328,11 @@ int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
         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;
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index e101c5bb9eda..6a4d3fa94042 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -365,7 +365,7 @@ extern int traceprobe_conflict_field_name(const char *name,
 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);
 
 /* Sum up total data length for dynamic arraies (strings) */
 static nokprobe_inline int