5.4-stable review patch. If anyone has any objections, please let me know.
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From: Roberto Sassu roberto.sassu@huawei.com
[ 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@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 --- 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 4f2a4ac8a82bb..d6a78c3548a55 100644 --- a/arch/um/drivers/line.c +++ b/arch/um/drivers/line.c @@ -673,24 +673,26 @@ 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: