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

commit ad9e202aa1ce571b1d7fed969d06f66067f8a086 upstream.

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.

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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 076bd41bf5ac916db1427b1ccb9ea926dc9f21e8..cdf1ec11c015c35bafdd9513770e2c18d209f19d 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -442,6 +442,8 @@ 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)
@@ -451,6 +453,8 @@ 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)