On Mon, Jan 07, 2019 at 10:39:41AM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 4.14-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From 169113ece0f29ebe884a6cfcf57c1ace04d8a36a Mon Sep 17 00:00:00 2001
> From: Will Deacon <will.deacon@xxxxxxx>
> Date: Thu, 3 Jan 2019 17:45:07 +0000
> Subject: [PATCH] arm64: compat: Avoid sending SIGILL for unallocated syscall
> numbers
>
> The ARM Linux kernel handles the EABI syscall numbers as follows:
>
> 0 - NR_SYSCALLS-1 : Invoke syscall via syscall table
> NR_SYSCALLS - 0xeffff : -ENOSYS (to be allocated in future)
> 0xf0000 - 0xf07ff : Private syscall or -ENOSYS if not allocated
> > 0xf07ff : SIGILL
>
> Our compat code gets this wrong and ends up sending SIGILL in response
> to all syscalls greater than NR_SYSCALLS which have a value greater
> than 0x7ff in the bottom 16 bits.
>
> Fix this by defining the end of the ARM private syscall region and
> checking the syscall number against that directly. Update the comment
> while we're at it.
Aha, looks like 532826f3712b ("arm64: Mirror arm for unimplemented compat
syscalls") wasn't CC'd for stable so the breakage it caused didn't
propagate to 4.14 or earlier.
I'll send a rebased version of the other patch in this series for 4.19
stable separately.
Will
