[4.19,BACKPORT] arm64: debug: Don't propagate UNKNOWN FAR into si_code for debug signals

Message ID 20190403103408.29209-1-will.deacon@arm.com
State New
Headers show
Series
  • [4.19,BACKPORT] arm64: debug: Don't propagate UNKNOWN FAR into si_code for debug signals
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Commit Message

Will Deacon April 3, 2019, 10:34 a.m.
Commit b9a4b9d084d978f80eb9210727c81804588b42ff upstream.

FAR_EL1 is UNKNOWN for all debug exceptions other than those caused by
taking a hardware watchpoint. Unfortunately, if a debug handler returns
a non-zero value, then we will propagate the UNKNOWN FAR value to
userspace via the si_addr field of the SIGTRAP siginfo_t.

Instead, let's set si_addr to take on the PC of the faulting instruction,
which we have available in the current pt_regs.

Cc: <stable@vger.kernel.org> # 4.19.y
Reviewed-by: Mark Rutland <mark.rutland@arm.com>

Signed-off-by: Will Deacon <will.deacon@arm.com>

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

---
 arch/arm64/mm/fault.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

-- 
2.11.0

Comments

Greg KH April 3, 2019, 1:56 p.m. | #1
On Wed, Apr 03, 2019 at 11:34:08AM +0100, Will Deacon wrote:
> Commit b9a4b9d084d978f80eb9210727c81804588b42ff upstream.

> 

> FAR_EL1 is UNKNOWN for all debug exceptions other than those caused by

> taking a hardware watchpoint. Unfortunately, if a debug handler returns

> a non-zero value, then we will propagate the UNKNOWN FAR value to

> userspace via the si_addr field of the SIGTRAP siginfo_t.

> 

> Instead, let's set si_addr to take on the PC of the faulting instruction,

> which we have available in the current pt_regs.

> 

> Cc: <stable@vger.kernel.org> # 4.19.y

> Reviewed-by: Mark Rutland <mark.rutland@arm.com>

> Signed-off-by: Will Deacon <will.deacon@arm.com>

> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

> ---

>  arch/arm64/mm/fault.c | 9 +++++----

>  1 file changed, 5 insertions(+), 4 deletions(-)


Thanks for all 5 of these patches, now queued up.

greg k-h

Patch

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 50b30ff30de4..a4c134677285 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -827,11 +827,12 @@  void __init hook_debug_fault_code(int nr,
 	debug_fault_info[nr].name	= name;
 }
 
-asmlinkage int __exception do_debug_exception(unsigned long addr,
+asmlinkage int __exception do_debug_exception(unsigned long addr_if_watchpoint,
 					      unsigned int esr,
 					      struct pt_regs *regs)
 {
 	const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
+	unsigned long pc = instruction_pointer(regs);
 	int rv;
 
 	/*
@@ -841,10 +842,10 @@  asmlinkage int __exception do_debug_exception(unsigned long addr,
 	if (interrupts_enabled(regs))
 		trace_hardirqs_off();
 
-	if (user_mode(regs) && instruction_pointer(regs) > TASK_SIZE)
+	if (user_mode(regs) && pc > TASK_SIZE)
 		arm64_apply_bp_hardening();
 
-	if (!inf->fn(addr, esr, regs)) {
+	if (!inf->fn(addr_if_watchpoint, esr, regs)) {
 		rv = 1;
 	} else {
 		struct siginfo info;
@@ -853,7 +854,7 @@  asmlinkage int __exception do_debug_exception(unsigned long addr,
 		info.si_signo = inf->sig;
 		info.si_errno = 0;
 		info.si_code  = inf->code;
-		info.si_addr  = (void __user *)addr;
+		info.si_addr  = (void __user *)pc;
 		arm64_notify_die(inf->name, regs, &info, esr);
 		rv = 0;
 	}