um: winch_interrupt() can happen inside of free_winch()

...  so set winch->fd to -1 before doing free_irq(), to avoid having
winch_interrupt() come from/during the latter and attempt to do
reactivate_fd() on something that's already gone.

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, 4 insertions, 2 deletions

diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index c5bff1ddeabc..91bf18941ca4 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -725,6 +725,8 @@ struct winch {
 
 static void free_winch(struct winch *winch, int free_irq_ok)
 {
+        int fd = winch->fd;
+        winch->fd = -1;
         if (free_irq_ok)
                 free_irq(WINCH_IRQ, winch);
 
@@ -732,8 +734,8 @@ static void free_winch(struct winch *winch, int free_irq_ok)
 
         if (winch->pid != -1)
                 os_kill_process(winch->pid, 1);
-        if (winch->fd != -1)
-                os_close_file(winch->fd);
+        if (fd != -1)
+                os_close_file(fd);
         if (winch->stack != 0)
                 free_stack(winch->stack, 0);
         kfree(winch);