From a0fbbd36c156b9f7b2276871d499c9943dfe5101 Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Thu, 7 Mar 2024 11:49:26 +0100 Subject: [PATCH] um: Add winch to winch_handlers before registering winch IRQ 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 Reviewed-by: Johannes Berg Signed-off-by: Richard Weinberger --- 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: