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um: Add winch to winch_handlers before registering winch IRQ

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[ Upstream commit a0fbbd36c1 ]

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: 42a359e31a ("uml: SIGIO support cleanup")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Roberto Sassu 2024-03-07 11:49:26 +01:00 committed by Greg Kroah-Hartman
parent e98f29bf0b
commit 434a06c38e
1 changed files with 8 additions and 6 deletions
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14
arch/um/drivers/line.c
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@ -673,24 +673,26 @@ void register_winch_irq(int fd, int tty_fd, int pid, struct tty_port *port,
goto cleanup; goto cleanup;
} }
*winch = ((struct winch) { .list = LIST_HEAD_INIT(winch->list), *winch = ((struct winch) { .fd = fd,
.fd = fd,
.tty_fd = tty_fd, .tty_fd = tty_fd,
.pid = pid, .pid = pid,
.port = port, .port = port,
.stack = stack }); .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, if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt,
IRQF_SHARED, "winch", winch) < 0) { IRQF_SHARED, "winch", winch) < 0) {
printk(KERN_ERR "register_winch_irq - failed to register " printk(KERN_ERR "register_winch_irq - failed to register "
"IRQ\n"); "IRQ\n");
spin_lock(&winch_handler_lock);
list_del(&winch->list);
spin_unlock(&winch_handler_lock);
goto out_free; goto out_free;
} }
spin_lock(&winch_handler_lock);
list_add(&winch->list, &winch_handlers);
spin_unlock(&winch_handler_lock);
return; return;
out_free: out_free: