[PATCH][RFC] [powerpc] arch_ptrace() uses of access_ok() are pointless

From: Al Viro
Date: Sun May 27 2018 - 18:34:13 EST


make it use copy_{from,to}_user(), rather than access_ok() +
__copy_...

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/ptrace.c | 22 +++++++---------------
1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index d23cf632edf0..d8b0fd2fa3aa 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -3081,27 +3081,19 @@ long arch_ptrace(struct task_struct *child, long request,
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif /* CONFIG_PPC_ADV_DEBUG_REGS */

- if (!access_ok(VERIFY_WRITE, datavp,
- sizeof(struct ppc_debug_info)))
+ if (unlikely(copy_to_user(datavp, &dbginfo,
+ sizeof(struct ppc_debug_info)))
return -EFAULT;
- ret = __copy_to_user(datavp, &dbginfo,
- sizeof(struct ppc_debug_info)) ?
- -EFAULT : 0;
- break;
+ return 0;
}

case PPC_PTRACE_SETHWDEBUG: {
struct ppc_hw_breakpoint bp_info;

- if (!access_ok(VERIFY_READ, datavp,
- sizeof(struct ppc_hw_breakpoint)))
- return -EFAULT;
- ret = __copy_from_user(&bp_info, datavp,
- sizeof(struct ppc_hw_breakpoint)) ?
- -EFAULT : 0;
- if (!ret)
- ret = ppc_set_hwdebug(child, &bp_info);
- break;
+ if (unlikely(copy_from_user(&bp_info, datavp,
+ sizeof(struct ppc_hw_breakpoint)))
+ return -EFAULT;
+ return ppc_set_hwdebug(child, &bp_info);
}

case PPC_PTRACE_DELHWDEBUG: {
--
2.11.0