um: fix races between line_open() and line_config()

Pull parse_chan_pair() call into setup_one_line(), under the mutex.
We really don't want open() to succeed before parse_chan_pair() had
been done (or after it has failed, BTW).  We also want "remove con<n>"
to free irqs, etc., same as "config con<n>=none".

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index 420e2c8..3a95498 100644 (file)
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -551,6 +551,9 @@ int parse_chan_pair(char *str, struct line *line, int device,
                INIT_LIST_HEAD(chans);
        }
 
+       if (!str)
+               return 0;
+
        out = strchr(str, ',');
        if (out != NULL) {
                in = str;

diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index dc7e216..1a8d659 100644 (file)
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -482,7 +482,7 @@ void close_lines(struct line *lines, int nlines)
 }
 
 static int setup_one_line(struct line *lines, int n, char *init,
-                         char **error_out)
+                         const struct chan_opts *opts, char **error_out)
 {
        struct line *line = &lines[n];
        int err = -EINVAL;
@@ -494,13 +494,28 @@ static int setup_one_line(struct line *lines, int n, char *init,
                goto out;
        }
 
-       if (!strcmp(init, "none"))
-               line->valid = 0;
-       else {
-               line->init_str = init;
+       if (!strcmp(init, "none")) {
+               if (line->valid) {
+                       line->valid = 0;
+                       kfree(line->init_str);
+                       parse_chan_pair(NULL, line, n, opts, error_out);
+                       err = 0;
+               }
+       } else {
+               char *new = kstrdup(init, GFP_KERNEL);
+               if (!new) {
+                       *error_out = "Failed to allocate memory";
+                       return -ENOMEM;
+               }
+               line->init_str = new;
                line->valid = 1;
+               err = parse_chan_pair(new, line, n, opts, error_out);
+               if (err) {
+                       line->init_str = NULL;
+                       line->valid = 0;
+                       kfree(new);
+               }
        }
-       err = 0;
 out:
        mutex_unlock(&line->count_lock);
        return err;
@@ -549,10 +564,8 @@ out:
 int line_config(struct line *lines, unsigned int num, char *str,
                const struct chan_opts *opts, char **error_out)
 {
-       struct line *line;
-       char *new;
        char *end;
-       int n, err;
+       int n;
 
        if (*str == '=') {
                *error_out = "Can't configure all devices from mconsole";
@@ -569,16 +582,7 @@ int line_config(struct line *lines, unsigned int num, char *str,
                return -EINVAL;
        }
 
-       new = kstrdup(end, GFP_KERNEL);
-       if (new == NULL) {
-               *error_out = "Failed to allocate memory";
-               return -ENOMEM;
-       }
-       err = setup_one_line(lines, n, new, error_out);
-       if (err)
-               return err;
-       line = &lines[n];
-       return parse_chan_pair(line->init_str, line, n, opts, error_out);
+       return setup_one_line(lines, n, end, opts, error_out);
 }
 
 int line_get_config(char *name, struct line *lines, unsigned int num, char *str,
@@ -633,7 +637,7 @@ int line_remove(struct line *lines, unsigned int num, int n, char **error_out)
                *error_out = "Device number out of range";
                return -EINVAL;
        }
-       return setup_one_line(lines, n, "none", error_out);
+       return setup_one_line(lines, n, "none", NULL, error_out);
 }
 
 struct tty_driver *register_lines(struct line_driver *line_driver,
@@ -688,15 +692,9 @@ void lines_init(struct line *lines, int nlines, struct chan_opts *opts)
                if (line->init_str == NULL)
                        continue;
 
-               line->init_str = kstrdup(line->init_str, GFP_KERNEL);
-               if (line->init_str == NULL)
-                       printk(KERN_ERR "lines_init - kstrdup returned NULL\n");
-
-               if (parse_chan_pair(line->init_str, line, i, opts, &error)) {
-                       printk(KERN_ERR "parse_chan_pair failed for "
+               if (setup_one_line(lines, i, line->init_str, opts, &error))
+                       printk(KERN_ERR "setup_one_line failed for "
                               "device %d : %s\n", i, error);
-                       line->valid = 0;
-               }
        }
 }