powerpc/ptrace: Fix setting 512B aligned breakpoints with PTRACE_SET_DEBUGREG

BugLink: http://bugs.launchpad.net/bugs/1807469
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@vger.kernel.org # v3.11+
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index f52ad5bb710960906b8ae61400688845e2811dd5..81750d9624abbd14164e2a740e43b4b7ea393b9f 100644 (file)
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -2362,6 +2362,7 @@ static int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
        /* 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);