The patch below does not apply to the 4.4-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.

Cc: stable@vger.kernel.org Cc: Dave Martin Dave.Martin@arm.com Reported-by: Pi-Hsun Shih pihsun@chromium.org Signed-off-by: Will Deacon will.deacon@arm.com

diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h index b13ca091f833..85d5c1026204 100644 --- a/arch/arm64/include/asm/unistd.h +++ b/arch/arm64/include/asm/unistd.h @@ -40,8 +40,9 @@ * The following SVCs are ARM private. */ #define __ARM_NR_COMPAT_BASE 0x0f0000 -#define __ARM_NR_compat_cacheflush (__ARM_NR_COMPAT_BASE+2) -#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE+5) +#define __ARM_NR_compat_cacheflush (__ARM_NR_COMPAT_BASE + 2) +#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) +#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)

#define __NR_compat_syscalls 399 #endif diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c index 32653d156747..a79db4e485a6 100644 --- a/arch/arm64/kernel/sys_compat.c +++ b/arch/arm64/kernel/sys_compat.c @@ -102,12 +102,12 @@ long compat_arm_syscall(struct pt_regs *regs)

default: /* - * Calls 9f00xx..9f07ff are defined to return -ENOSYS + * Calls 0xf0xxx..0xf07ff are defined to return -ENOSYS * if not implemented, rather than raising SIGILL. This * way the calling program can gracefully determine whether * a feature is supported. */ - if ((no & 0xffff) <= 0x7ff) + if (no < __ARM_NR_COMPAT_END) return -ENOSYS; break; }