um: fix free_winch() mess

while not doing free_irq() from irq handler is commendable, kfree() on the
data passed to said handler before free_irq() is Not Good(tm).  Freeing
the stack it's being run on is also not nice...  Solution: delay actually
freeing stuff.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 24 insertions, 14 deletions

diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 91bf18941ca4..364c8a15c4c3 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -721,43 +721,53 @@ struct winch {
         int pid;
         struct tty_struct *tty;
         unsigned long stack;
+        struct work_struct work;
 };
 
-static void free_winch(struct winch *winch, int free_irq_ok)
+static void __free_winch(struct work_struct *work)
 {
-        int fd = winch->fd;
-        winch->fd = -1;
-        if (free_irq_ok)
-                free_irq(WINCH_IRQ, winch);
-
-        list_del(&winch->list);
+        struct winch *winch = container_of(work, struct winch, work);
+        free_irq(WINCH_IRQ, winch);
 
         if (winch->pid != -1)
                 os_kill_process(winch->pid, 1);
-        if (fd != -1)
-                os_close_file(fd);
         if (winch->stack != 0)
                 free_stack(winch->stack, 0);
         kfree(winch);
 }
 
+static void free_winch(struct winch *winch)
+{
+        int fd = winch->fd;
+        winch->fd = -1;
+        if (fd != -1)
+                os_close_file(fd);
+        list_del(&winch->list);
+        __free_winch(&winch->work);
+}
+
 static irqreturn_t winch_interrupt(int irq, void *data)
 {
         struct winch *winch = data;
         struct tty_struct *tty;
         struct line *line;
+        int fd = winch->fd;
         int err;
         char c;
 
-        if (winch->fd != -1) {
-                err = generic_read(winch->fd, &c, NULL);
+        if (fd != -1) {
+                err = generic_read(fd, &c, NULL);
                 if (err < 0) {
                         if (err != -EAGAIN) {
+                                winch->fd = -1;
+                                list_del(&winch->list);
+                                os_close_file(fd);
                                 printk(KERN_ERR "winch_interrupt : "
                                        "read failed, errno = %d\n", -err);
                                 printk(KERN_ERR "fd %d is losing SIGWINCH "
                                        "support\n", winch->tty_fd);
-                                free_winch(winch, 0);
+                                INIT_WORK(&winch->work, __free_winch);
+                                schedule_work(&winch->work);
                                 return IRQ_HANDLED;
                         }
                         goto out;
@@ -829,7 +839,7 @@ static void unregister_winch(struct tty_struct *tty)
         list_for_each_safe(ele, next, &winch_handlers) {
                 winch = list_entry(ele, struct winch, list);
                 if (winch->tty == tty) {
-                        free_winch(winch, 1);
+                        free_winch(winch);
                         break;
                 }
         }
@@ -845,7 +855,7 @@ static void winch_cleanup(void)
 
         list_for_each_safe(ele, next, &winch_handlers) {
                 winch = list_entry(ele, struct winch, list);
-                free_winch(winch, 1);
+                free_winch(winch);
         }
 
         spin_unlock(&winch_handler_lock);