| Message ID | 20240307104926.3531358-1-roberto.sassu@huaweicloud.com |
|---|---|
| State | New |
| Headers | show |
| Series | um: Add winch to winch_handlers before registering winch IRQ | expand |
On Thu, 2024-03-07 at 11:49 +0100, Roberto Sassu wrote: > From: Roberto Sassu <roberto.sassu@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.sassu@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. 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:
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.sassu@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.sassu@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:
On Thu, 2024-03-07 at 11:49 +0100, Roberto Sassu wrote: > From: Roberto Sassu <roberto.sassu@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. > Reviewed-by: Johannes Berg <johannes@sipsolutions.net> johannes
On Thu, 2024-03-28 at 09:25 +0100, Johannes Berg wrote: > On Thu, 2024-03-07 at 11:49 +0100, Roberto Sassu wrote: > > From: Roberto Sassu <roberto.sassu@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. > > > > Reviewed-by: Johannes Berg <johannes@sipsolutions.net> Thank you! Richard, are you going to pick this up? Thanks Roberto
----- Ursprüngliche Mail ----- > Von: "Roberto Sassu" <roberto.sassu@huaweicloud.com> > An: "Johannes Berg" <johannes@sipsolutions.net>, "richard" <richard@nod.at>, "anton ivanov" > <anton.ivanov@cambridgegreys.com> > CC: "linux-kernel" <linux-kernel@vger.kernel.org>, "linux-um" <linux-um@lists.infradead.org>, "Roberto Sassu" > <roberto.sassu@huawei.com> > Gesendet: Dienstag, 23. April 2024 09:22:31 > Betreff: Re: [PATCH] um: Add winch to winch_handlers before registering winch IRQ > On Thu, 2024-03-28 at 09:25 +0100, Johannes Berg wrote: >> On Thu, 2024-03-07 at 11:49 +0100, Roberto Sassu wrote: >> > From: Roberto Sassu <roberto.sassu@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. >> > >> >> Reviewed-by: Johannes Berg <johannes@sipsolutions.net> > > Thank you! Richard, are you going to pick this up? Yes, it's already in my local queue. Thanks, //richard
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: