arm64: debug: Ensure debug handlers check triggering exception level
commit 6bd288569b50bc89fa5513031086746968f585cb upstream.
Debug exception handlers may be called for exceptions generated both by
user and kernel code. In many cases, this is checked explicitly, but
in other cases things either happen to work by happy accident or they
go slightly wrong. For example, executing 'brk #4' from userspace will
enter the kprobes code and be ignored, but the instruction will be
retried forever in userspace instead of delivering a SIGTRAP.
Fix this issue in the most stable-friendly fashion by simply adding
explicit checks of the triggering exception level to all of our debug
exception handlers.
Cc: <stable@vger.kernel.org>
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
index e017a94..72a660a 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c
@@ -231,24 +231,33 @@
static int kgdb_brk_fn(struct pt_regs *regs, unsigned int esr)
{
+ if (user_mode(regs))
+ return DBG_HOOK_ERROR;
+
kgdb_handle_exception(1, SIGTRAP, 0, regs);
- return 0;
+ return DBG_HOOK_HANDLED;
}
NOKPROBE_SYMBOL(kgdb_brk_fn)
static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int esr)
{
+ if (user_mode(regs))
+ return DBG_HOOK_ERROR;
+
compiled_break = 1;
kgdb_handle_exception(1, SIGTRAP, 0, regs);
- return 0;
+ return DBG_HOOK_HANDLED;
}
NOKPROBE_SYMBOL(kgdb_compiled_brk_fn);
static int kgdb_step_brk_fn(struct pt_regs *regs, unsigned int esr)
{
+ if (user_mode(regs))
+ return DBG_HOOK_ERROR;
+
kgdb_handle_exception(1, SIGTRAP, 0, regs);
- return 0;
+ return DBG_HOOK_HANDLED;
}
NOKPROBE_SYMBOL(kgdb_step_brk_fn);
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index d2b1b62..17f6471 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -450,6 +450,9 @@
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
int retval;
+ if (user_mode(regs))
+ return DBG_HOOK_ERROR;
+
/* return error if this is not our step */
retval = kprobe_ss_hit(kcb, instruction_pointer(regs));
@@ -466,6 +469,9 @@
int __kprobes
kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
{
+ if (user_mode(regs))
+ return DBG_HOOK_ERROR;
+
kprobe_handler(regs);
return DBG_HOOK_HANDLED;
}