From 52d7523d84d534c241ebac5ac89f5c0a6cb51e41 Mon Sep 17 00:00:00 2001 From: EunTaik Lee Date: Tue, 16 Feb 2016 04:44:35 +0000 Subject: [PATCH] arm64: mm: allow the kernel to handle alignment faults on user accesses Although we don't expect to take alignment faults on access to normal memory, misbehaving (i.e. buggy) user code can pass MMIO pointers into system calls, leading to things like get_user accessing device memory. Rather than OOPS the kernel, allow any exception fixups to run and return something like -EFAULT back to userspace. This makes the behaviour more consistent with userspace, even though applications with access to device mappings can easily cause other issues if they try hard enough. Acked-by: Catalin Marinas Signed-off-by: Eun Taik Lee [will: dropped __kprobes annotation and rewrote commit mesage] Signed-off-by: Will Deacon --- arch/arm64/mm/fault.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 92ddac1e8ca2..abe2a9542b3a 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -371,6 +371,13 @@ static int __kprobes do_translation_fault(unsigned long addr, return 0; } +static int do_alignment_fault(unsigned long addr, unsigned int esr, + struct pt_regs *regs) +{ + do_bad_area(addr, esr, regs); + return 0; +} + /* * This abort handler always returns "fault". */ @@ -418,7 +425,7 @@ static struct fault_info { { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" }, { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" }, { do_bad, SIGBUS, 0, "unknown 32" }, - { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" }, + { do_alignment_fault, SIGBUS, BUS_ADRALN, "alignment fault" }, { do_bad, SIGBUS, 0, "unknown 34" }, { do_bad, SIGBUS, 0, "unknown 35" }, { do_bad, SIGBUS, 0, "unknown 36" },