[RFC PATCH v1 1/2] x86/mm: use VMA lock for kernel faults on user addresses

[Barry Song (Xiaomi)]

Use the VMA lock for kernel faults on user addresses. This also
makes the existing code below meaningful:

  /* Quick path to respond to signals */
  if (fault_signal_pending(fault, regs)) {
          if (!user_mode(regs))
                  kernelmode_fixup_or_oops(regs, error_code, address,
                                           SIGBUS, BUS_ADRERR,
                                           ARCH_DEFAULT_PKEY);
          return;
  }

Right now, the code above is dead because !user_mode always
takes the mmap_lock path.

Co-developed-by: Bo Zhang <zhangbo56 at xiaomi.com>
Signed-off-by: Bo Zhang <zhangbo56 at xiaomi.com>
Signed-off-by: Barry Song (Xiaomi) <baohua at kernel.org>
---
 arch/x86/mm/fault.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 45b99c3b1442..c22b74e0eeaf 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1328,9 +1328,6 @@ void do_user_addr_fault(struct pt_regs *regs,
 	}
 #endif
 
-	if (!(flags & FAULT_FLAG_USER))
-		goto lock_mmap;
-
 	vma = lock_vma_under_rcu(mm, address);
 	if (!vma)
 		goto lock_mmap;
-- 
2.39.3 (Apple Git-146)