On Mon, Jan 07, 2019 at 10:39:41AM +0100, gregkh@linuxfoundation.org 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@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 169113ece0f29ebe884a6cfcf57c1ace04d8a36a Mon Sep 17 00:00:00 2001 From: Will Deacon will.deacon@arm.com 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