On 3/7/2024 1:43 PM, Roberto Sassu wrote:
On Thu, 2024-03-07 at 11:49 +0100, Roberto Sassu wrote:
From: Roberto Sassu <roberto.sa...@huawei.com>
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.
Signed-off-by: Roberto Sassu <roberto.sa...@huawei.com>
Fixes: 42a359e31a0e ("uml: SIGIO support cleanup")
I see that before that commit there was the same ordering (list_add()
before um_request_irq()).
Failure from um_request_irq() should not result in executing
winch_interrupt() which could call list_del() itself. Then, it should
be fine to delete the winch in the error path.
Richard, did you have time to look at this?
Thanks
Roberto
Roberto
---
arch/um/drivers/line.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index ffc5cb92fa36..d82bc3fdb86e 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -676,24 +676,26 @@ 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:
