From 73ac5d6a2b6ac3ae8d1e1818f3e9946f97489bc9 Mon Sep 17 00:00:00 2001 From: Thomas Garnier Date: Wed, 14 Jun 2017 18:12:02 -0700 Subject: arm/syscalls: Check address limit on user-mode return Ensure the address limit is a user-mode segment before returning to user-mode. Otherwise a process can corrupt kernel-mode memory and elevate privileges [1]. The set_fs function sets the TIF_SETFS flag to force a slow path on return. In the slow path, the address limit is checked to be USER_DS if needed. The TIF_SETFS flag is added to _TIF_WORK_MASK shifting _TIF_SYSCALL_WORK for arm instruction immediate support. The global work mask is too big to used on a single instruction so adapt ret_fast_syscall. [1] https://bugs.chromium.org/p/project-zero/issues/detail?id=990 Signed-off-by: Thomas Garnier Signed-off-by: Thomas Gleixner Cc: Mark Rutland Cc: kernel-hardening@lists.openwall.com Cc: Catalin Marinas Cc: Will Deacon Cc: David Howells Cc: Dave Hansen Cc: Miroslav Benes Cc: Chris Metcalf Cc: Pratyush Anand Cc: Russell King Cc: Petr Mladek Cc: Rik van Riel Cc: Kees Cook Cc: Arnd Bergmann Cc: Al Viro Cc: Andy Lutomirski Cc: Josh Poimboeuf Cc: linux-arm-kernel@lists.infradead.org Cc: Will Drewry Cc: linux-api@vger.kernel.org Cc: Oleg Nesterov Cc: Andy Lutomirski Cc: Paolo Bonzini Link: http://lkml.kernel.org/r/20170615011203.144108-2-thgarnie@google.com --- arch/arm/kernel/entry-common.S | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'arch/arm/kernel/entry-common.S') diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index eb5cd77bf1d8..e33c32d56193 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -41,7 +41,9 @@ ret_fast_syscall: UNWIND(.cantunwind ) disable_irq_notrace @ disable interrupts ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing - tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK + tst r1, #_TIF_SYSCALL_WORK + bne fast_work_pending + tst r1, #_TIF_WORK_MASK bne fast_work_pending /* perform architecture specific actions before user return */ @@ -67,12 +69,15 @@ ret_fast_syscall: str r0, [sp, #S_R0 + S_OFF]! @ save returned r0 disable_irq_notrace @ disable interrupts ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing - tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK + tst r1, #_TIF_SYSCALL_WORK + bne fast_work_pending + tst r1, #_TIF_WORK_MASK beq no_work_pending UNWIND(.fnend ) ENDPROC(ret_fast_syscall) /* Slower path - fall through to work_pending */ +fast_work_pending: #endif tst r1, #_TIF_SYSCALL_WORK -- cgit v1.2.1