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: Willy Tarreau <w@1wt.eu>

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 777763d701d832b7600ea14a8a6f1cef5b452528..015775ad76043be69ed184c39bc31ddd81917952 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -464,6 +464,8 @@ 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)
@@ -473,6 +475,8 @@ 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)