This is a note to let you know that I've just added the patch titled
arm64: hw_breakpoint: fix watchpoint matching for tagged pointers
to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-hw_breakpoint-fix-watchpoint-matching-for-tagged-pointers.patch
and it can be found in the queue-4.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7dcd9dd8cebe9fa626af7e2358d03a37041a70fb Mon Sep 17 00:00:00 2001
From: Kristina Martsenko <kristina.martsenko@xxxxxxx>
Date: Wed, 3 May 2017 16:37:46 +0100
Subject: arm64: hw_breakpoint: fix watchpoint matching for tagged pointers
From: Kristina Martsenko <kristina.martsenko@xxxxxxx>
commit 7dcd9dd8cebe9fa626af7e2358d03a37041a70fb upstream.
When we take a watchpoint exception, the address that triggered the
watchpoint is found in FAR_EL1. We compare it to the address of each
configured watchpoint to see which one was hit.
The configured watchpoint addresses are untagged, while the address in
FAR_EL1 will have an address tag if the data access was done using a
tagged address. The tag needs to be removed to compare the address to
the watchpoints.
Currently we don't remove it, and as a result can report the wrong
watchpoint as being hit (specifically, always either the highest TTBR0
watchpoint or lowest TTBR1 watchpoint). This patch removes the tag.
Fixes: d50240a5f6ce ("arm64: mm: permit use of tagged pointers at EL0")
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Kristina Martsenko <kristina.martsenko@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/include/asm/uaccess.h | 6 +++---
arch/arm64/kernel/hw_breakpoint.c | 3 +++
2 files changed, 6 insertions(+), 3 deletions(-)
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -107,9 +107,9 @@ static inline void set_fs(mm_segment_t f
})
/*
- * When dealing with data aborts or instruction traps we may end up with
- * a tagged userland pointer. Clear the tag to get a sane pointer to pass
- * on to access_ok(), for instance.
+ * When dealing with data aborts, watchpoints, or instruction traps we may end
+ * up with a tagged userland pointer. Clear the tag to get a sane pointer to
+ * pass on to access_ok(), for instance.
*/
#define untagged_addr(addr) sign_extend64(addr, 55)
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -36,6 +36,7 @@
#include <asm/traps.h>
#include <asm/cputype.h>
#include <asm/system_misc.h>
+#include <asm/uaccess.h>
/* Breakpoint currently in use for each BRP. */
static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
@@ -721,6 +722,8 @@ static u64 get_distance_from_watchpoint(
u64 wp_low, wp_high;
u32 lens, lene;
+ addr = untagged_addr(addr);
+
lens = __ffs(ctrl->len);
lene = __fls(ctrl->len);
Patches currently in stable-queue which might be from kristina.martsenko@xxxxxxx are
queue-4.11/arm64-hw_breakpoint-fix-watchpoint-matching-for-tagged-pointers.patch
queue-4.11/arm64-entry-improve-data-abort-handling-of-tagged-pointers.patch
queue-4.11/arm64-documentation-document-tagged-pointer-stack-constraints.patch
queue-4.11/arm64-traps-fix-userspace-cache-maintenance-emulation-on-a-tagged-pointer.patch