From: Will Deacon <will.deacon@arm.com>
Date: Tue, 31 Oct 2017 15:56:11 +0000 (+0000)
Subject: arm64: Don't walk page table for user faults in do_mem_abort
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=80b6eb04b5d05a472a37ae33647b213dd04e59b6;p=linux.git

arm64: Don't walk page table for user faults in do_mem_abort

Commit 42dbf54e8890 ("arm64: consistently log ESR and page table")
dumps page table entries for user faults hitting do_bad entries in the
fault handler table. Whilst this shouldn't really happen in practice,
it's not beyond the realms of possibility if e.g. running an old kernel
on a new CPU.

Generally, we want to avoid exposing physical addresses under the control
of userspace (see commit bf396c09c24 ("arm64: mm: don't print out page
table entries on EL0 faults")), so walk the page tables only on exceptions
from EL1.

Reported-by: Kristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 6ee22cd8a2494..a2a1a6c83da19 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -698,7 +698,8 @@ asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
 
 	mem_abort_decode(esr);
 
-	show_pte(addr);
+	if (!user_mode(regs))
+		show_pte(addr);
 
 	info.si_signo = inf->sig;
 	info.si_errno = 0;