tracing: Make -ENOMEM the default error for parse_synth_field()

parse_synth_field() returns a pointer and requires that errors get
surrounded by ERR_PTR(). The ret variable is initialized to zero, but should
never be used as zero, and if it is, it could cause a false return code and
produce a NULL pointer dereference. It makes no sense to set ret to zero.

Set ret to -ENOMEM (the most common error case), and have any other errors
set it to something else. This removes the need to initialize ret on *every*
error branch.

Fixes: 761a8c58db6b ("tracing, synthetic events: Replace buggy strcat() with seq_buf operations")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 84b7cab..881df99 100644 (file)
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -584,7 +584,7 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
 {
        struct synth_field *field;
        const char *prefix = NULL, *field_type = argv[0], *field_name, *array;
-       int len, ret = 0;
+       int len, ret = -ENOMEM;
        struct seq_buf s;
        ssize_t size;
 
@@ -617,10 +617,9 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
                len--;
 
        field->name = kmemdup_nul(field_name, len, GFP_KERNEL);
-       if (!field->name) {
-               ret = -ENOMEM;
+       if (!field->name)
                goto free;
-       }
+
        if (!is_good_name(field->name)) {
                synth_err(SYNTH_ERR_BAD_NAME, errpos(field_name));
                ret = -EINVAL;
@@ -638,10 +637,9 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
                len += strlen(prefix);
 
        field->type = kzalloc(len, GFP_KERNEL);
-       if (!field->type) {
-               ret = -ENOMEM;
+       if (!field->type)
                goto free;
-       }
+
        seq_buf_init(&s, field->type, len);
        if (prefix)
                seq_buf_puts(&s, prefix);
@@ -653,6 +651,7 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
        }
        if (WARN_ON_ONCE(!seq_buf_buffer_left(&s)))
                goto free;
+
        s.buffer[s.len] = '\0';
 
        size = synth_field_size(field->type);
@@ -666,10 +665,8 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
 
                        len = sizeof("__data_loc ") + strlen(field->type) + 1;
                        type = kzalloc(len, GFP_KERNEL);
-                       if (!type) {
-                               ret = -ENOMEM;
+                       if (!type)
                                goto free;
-                       }
 
                        seq_buf_init(&s, type, len);
                        seq_buf_puts(&s, "__data_loc ");