Re: [rgushchin:fix_vmstats 199/221] lib/strncpy_from_user.c:112:42: warning: passing argument 1 of 'untagged_addr' makes integer from pointer without a cast

[Andrey Konovalov <andreyknvl@google.com>]

On Tue, Aug 13, 2019 at 4:01 PM kbuild test robot <lkp@intel.com> wrote:
>
> tree:   https://github.com/rgushchin/linux.git fix_vmstats
> head:   4ec858b5201ae067607e82706b36588631c1b990
> commit: f198eb8345ed9cef77b65d1c0edffba3fa3f6d2a [199/221] lib: untag user pointers in strn*_user
> config: sparc64-allmodconfig (attached as .config)
> compiler: sparc64-linux-gcc (GCC) 7.4.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         git checkout f198eb8345ed9cef77b65d1c0edffba3fa3f6d2a
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.4.0 make.cross ARCH=sparc64
>
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>):
>
>    lib/strncpy_from_user.c: In function 'strncpy_from_user':
> >> lib/strncpy_from_user.c:112:42: warning: passing argument 1 of 'untagged_addr' makes integer from pointer without a cast [-Wint-conversion]
>      src_addr = (unsigned long)untagged_addr(src);
>                                              ^~~
>    In file included from arch/sparc/include/asm/pgtable.h:5:0,
>                     from include/linux/mm.h:99,
>                     from lib/strncpy_from_user.c:9:
>    arch/sparc/include/asm/pgtable_64.h:1081:29: note: expected 'long unsigned int' but argument is of type 'const char *'
>     static inline unsigned long untagged_addr(unsigned long start)
>                                 ^~~~~~~~~~~~~
> --
>    lib/strnlen_user.c: In function 'strnlen_user':
> >> lib/strnlen_user.c:113:42: warning: passing argument 1 of 'untagged_addr' makes integer from pointer without a cast [-Wint-conversion]
>      src_addr = (unsigned long)untagged_addr(str);
>                                              ^~~
>    In file included from arch/sparc/include/asm/pgtable.h:5:0,
>                     from include/linux/mm.h:99,
>                     from lib/strnlen_user.c:5:
>    arch/sparc/include/asm/pgtable_64.h:1081:29: note: expected 'long unsigned int' but argument is of type 'const char *'
>     static inline unsigned long untagged_addr(unsigned long start)
>                                 ^~~~~~~~~~~~~

This is caused by the difference in untagged_addr() definitions for
sparc and arm64. untagged_addr() for arm64 uses __typeof__ to avoid
casting in places where it is used. Perhaps we should do something
similar for sparc:

diff --git a/arch/sparc/include/asm/pgtable_64.h
b/arch/sparc/include/asm/pgtable_64.h
index 1599de730532..2c4cd82066cb 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -1078,7 +1078,7 @@ static inline int io_remap_pfn_range(struct
vm_area_struct *vma,
 }
 #define io_remap_pfn_range io_remap_pfn_range

-static inline unsigned long untagged_addr(unsigned long start)
+static inline unsigned long __untagged_addr(unsigned long start)
 {
        if (adi_capable()) {
                long addr = start;
@@ -1098,7 +1098,8 @@ static inline unsigned long
untagged_addr(unsigned long start)

        return start;
 }
-#define untagged_addr untagged_addr
+#define untagged_addr(addr) \
+       ((__typeof__(addr))(__untagged_addr((unsigned long)(addr)))

 static inline bool pte_access_permitted(pte_t pte, bool write)
 {

Christoph, WDYT?

>
> vim +/untagged_addr +112 lib/strncpy_from_user.c
>
>     85
>     86  /**
>     87   * strncpy_from_user: - Copy a NUL terminated string from userspace.
>     88   * @dst:   Destination address, in kernel space.  This buffer must be at
>     89   *         least @count bytes long.
>     90   * @src:   Source address, in user space.
>     91   * @count: Maximum number of bytes to copy, including the trailing NUL.
>     92   *
>     93   * Copies a NUL-terminated string from userspace to kernel space.
>     94   *
>     95   * On success, returns the length of the string (not including the trailing
>     96   * NUL).
>     97   *
>     98   * If access to userspace fails, returns -EFAULT (some data may have been
>     99   * copied).
>    100   *
>    101   * If @count is smaller than the length of the string, copies @count bytes
>    102   * and returns @count.
>    103   */
>    104  long strncpy_from_user(char *dst, const char __user *src, long count)
>    105  {
>    106          unsigned long max_addr, src_addr;
>    107
>    108          if (unlikely(count <= 0))
>    109                  return 0;
>    110
>    111          max_addr = user_addr_max();
>  > 112          src_addr = (unsigned long)untagged_addr(src);
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation