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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 143f770247c2dd0013335411f9ef6481970c6ed7..8eedeef375d606961db5235b8d3c60d2eb184d51 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -550,6 +550,8 @@ 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)
@@ -559,6 +561,8 @@ 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)