arm64/ptrace: Reject attempts to set incomplete hardware breakpoint fields

We cannot preserve partial fields for hardware breakpoints, because
the values written by userspace to the hardware breakpoint
registers can't subsequently be recovered intact from the hardware.

So, just reject attempts to write incomplete fields with -EINVAL.

Cc: <stable@vger.kernel.org> # 3.7.x-
Fixes: 478fcb2cdb23 ("arm64: Debugging support")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Will Deacon <Will.Deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 91c4719dfc005179a6f4a03609c228e3082e1174..a22161ccf4470afa644850cd47c18b561da0d0e1 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -551,6 +551,8 @@ static int hw_break_set(struct task_struct *target,
        /* (address, ctrl) registers */
        limit = regset->n * regset->size;
        while (count && offset < limit) {
+               if (count < PTRACE_HBP_ADDR_SZ)
+                       return -EINVAL;
                ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &addr,
                                         offset, offset + PTRACE_HBP_ADDR_SZ);
                if (ret)
@@ -560,6 +562,8 @@ static int hw_break_set(struct task_struct *target,
                        return ret;
                offset += PTRACE_HBP_ADDR_SZ;
 
+               if (!count)
+                       break;
                ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ctrl,
                                         offset, offset + PTRACE_HBP_CTRL_SZ);
                if (ret)