On Thu, Jan 21, 2021 at 05:04:16PM +0100, Thomas Bogendoerfer wrote:
> When there's a fatal signal pending, MIPS's do_page_fault()
> implementation returns. The intent is that we'll return to the
> faulting userspace instruction, delivering the signal on the way.
>
> However, if we take a fatal signal during fixing up a uaccess, this
> results in a return to the faulting kernel instruction, which will be
> instantly retried, resulting in the same fault being taken forever. As
> the task never reaches userspace, the signal is not delivered, and the
> task is left unkillable. While the task is stuck in this state, it can
> inhibit the forward progress of the system.
>
> To avoid this, we must ensure that when a fatal signal is pending, we
> apply any necessary fixup for a faulting kernel instruction. Thus we
> will return to an error path, and it is up to that code to make forward
> progress towards delivering the fatal signal.
>
> [ Description taken from commit 746a272e4414 ("ARM: 8692/1: mm: abort
> uaccess retries upon fatal signal") ]
>
> Signed-off-by: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> ---
> arch/mips/mm/fault.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
applied to mips-next.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
