[PATCH 4.9 025/101] powerpc/ptrace: Fix setting 512B aligned breakpoints with PTRACE_SET_DEBUGREG

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Neuling <mikey@xxxxxxxxxxx>

commit 4f7c06e26ec9cf7fe9f0c54dc90079b6a4f4b2c3 upstream.

In commit e2a800beaca1 ("powerpc/hw_brk: Fix off by one error when
validating DAWR region end") we fixed setting the DAWR end point to
its max value via PPC_PTRACE_SETHWDEBUG. Unfortunately we broke
PTRACE_SET_DEBUGREG when setting a 512 byte aligned breakpoint.

PTRACE_SET_DEBUGREG currently sets the length of the breakpoint to
zero (memset() in hw_breakpoint_init()). This worked with
arch_validate_hwbkpt_settings() before the above patch was applied but
is now broken if the breakpoint is 512byte aligned.

This sets the length of the breakpoint to 8 bytes when using
PTRACE_SET_DEBUGREG.

Fixes: e2a800beaca1 ("powerpc/hw_brk: Fix off by one error when validating DAWR region end")
Cc: stable@xxxxxxxxxxxxxxx # v3.11+
Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/powerpc/kernel/ptrace.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -2380,6 +2380,7 @@ static int ptrace_set_debugreg(struct ta
 	/* Create a new breakpoint request if one doesn't exist already */
 	hw_breakpoint_init(&attr);
 	attr.bp_addr = hw_brk.address;
+	attr.bp_len = 8;
 	arch_bp_generic_fields(hw_brk.type,
 			       &attr.bp_type);