This is a note to let you know that I've just added the patch titled
um: Add winch to winch_handlers before registering winch IRQ
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
um-add-winch-to-winch_handlers-before-registering-wi.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 62db8e8649be5cda30e0952121e074fa22dbe21f
Author: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
Date: Thu Mar 7 11:49:26 2024 +0100
um: Add winch to winch_handlers before registering winch IRQ
[ Upstream commit a0fbbd36c156b9f7b2276871d499c9943dfe5101 ]
Registering a winch IRQ is racy, an interrupt may occur before the winch is
added to the winch_handlers list.
If that happens, register_winch_irq() adds to that list a winch that is
scheduled to be (or has already been) freed, causing a panic later in
winch_cleanup().
Avoid the race by adding the winch to the winch_handlers list before
registering the IRQ, and rolling back if um_request_irq() fails.
Fixes: 42a359e31a0e ("uml: SIGIO support cleanup")
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
Reviewed-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Richard Weinberger <richard@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 7e524efed5848..71e26488dfde2 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -683,24 +683,26 @@ void register_winch_irq(int fd, int tty_fd, int pid, struct tty_port *port,
goto cleanup;
}
- *winch = ((struct winch) { .list = LIST_HEAD_INIT(winch->list),
- .fd = fd,
+ *winch = ((struct winch) { .fd = fd,
.tty_fd = tty_fd,
.pid = pid,
.port = port,
.stack = stack });
+ spin_lock(&winch_handler_lock);
+ list_add(&winch->list, &winch_handlers);
+ spin_unlock(&winch_handler_lock);
+
if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt,
IRQF_SHARED, "winch", winch) < 0) {
printk(KERN_ERR "register_winch_irq - failed to register "
"IRQ\n");
+ spin_lock(&winch_handler_lock);
+ list_del(&winch->list);
+ spin_unlock(&winch_handler_lock);
goto out_free;
}
- spin_lock(&winch_handler_lock);
- list_add(&winch->list, &winch_handlers);
- spin_unlock(&winch_handler_lock);
-
return;
out_free:
