Hi Kangjie,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on pm/linux-next]
[also build test WARNING on v4.20 next-20181224]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]

url:    
https://github.com/0day-ci/linux/commits/Kangjie-Lu/acpi-fix-a-potential-inconsistency-caused-by-double-fetch/20181226-054721
base:   https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git 
linux-next
config: i386-randconfig-c0-12260412 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   In file included from include/linux/init.h:5:0,
                    from drivers/acpi/custom_method.c:5:
   drivers/acpi/custom_method.c: In function 'cm_write':
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:58:30: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                 ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   arch/x86/include/asm/uaccess.h:174:11: note: in expansion of macro 
'__inttype'
     register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);  \
              ^~~~~~~~~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   arch/x86/include/asm/uaccess.h:138:12: error: first argument to 
'__builtin_choose_expr' not a constant
    __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
               ^
   include/linux/compiler.h:58:30: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                 ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   arch/x86/include/asm/uaccess.h:174:11: note: in expansion of macro 
'__inttype'
     register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);  \
              ^~~~~~~~~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:58:30: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                 ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:58:30: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                 ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:58:30: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                 ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:58:42: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                             ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   arch/x86/include/asm/uaccess.h:174:11: note: in expansion of macro 
'__inttype'
     register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);  \
              ^~~~~~~~~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   arch/x86/include/asm/uaccess.h:138:12: error: first argument to 
'__builtin_choose_expr' not a constant
    __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
               ^
   include/linux/compiler.h:58:42: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                             ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   arch/x86/include/asm/uaccess.h:174:11: note: in expansion of macro 
'__inttype'
     register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);  \
              ^~~~~~~~~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:58:42: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                             ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:58:42: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                             ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:58:42: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                             ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:69:16: note: in definition of macro '__trace_if'
      ______r = !!(cond);     \
                   ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   arch/x86/include/asm/uaccess.h:174:11: note: in expansion of macro 
'__inttype'
     register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);  \
              ^~~~~~~~~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   arch/x86/include/asm/uaccess.h:138:12: error: first argument to 
'__builtin_choose_expr' not a constant
    __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
               ^
   include/linux/compiler.h:69:16: note: in definition of macro '__trace_if'
      ______r = !!(cond);     \
                   ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   arch/x86/include/asm/uaccess.h:174:11: note: in expansion of macro 
'__inttype'
     register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);  \
              ^~~~~~~~~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:69:16: note: in definition of macro '__trace_if'
      ______r = !!(cond);     \
                   ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:69:16: note: in definition of macro '__trace_if'
      ______r = !!(cond);     \
                   ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:36:42: error: request for member 'length' in 
something not a structure or union
        &(struct acpi_table_header *)user_buf->length))
                                             ^
   include/linux/compiler.h:69:16: note: in definition of macro '__trace_if'
      ______r = !!(cond);     \
                   ^~~~
>> drivers/acpi/custom_method.c:35:3: note: in expansion of macro 'if'
      if (get_user(max_size,
      ^~
   drivers/acpi/custom_method.c:35:7: note: in expansion of macro 'get_user'
      if (get_user(max_size,
          ^~~~~~~~
   drivers/acpi/custom_method.c:59:45: error: request for member 'length' in 
something not a structure or union
     (struct acpi_table_header *)(buf + (*ppos))->length = max_size;
                                                ^~

vim +/if +35 drivers/acpi/custom_method.c

   > 5  #include <linux/init.h>
     6  #include <linux/module.h>
     7  #include <linux/kernel.h>
     8  #include <linux/uaccess.h>
     9  #include <linux/debugfs.h>
    10  #include <linux/acpi.h>
    11  
    12  #include "internal.h"
    13  
    14  #define _COMPONENT              ACPI_SYSTEM_COMPONENT
    15  ACPI_MODULE_NAME("custom_method");
    16  MODULE_LICENSE("GPL");
    17  
    18  static struct dentry *cm_dentry;
    19  
    20  /* /sys/kernel/debug/acpi/custom_method */
    21  
    22  static ssize_t cm_write(struct file *file, const char __user * user_buf,
    23                          size_t count, loff_t *ppos)
    24  {
    25          static char *buf;
    26          static u32 max_size;
    27          static u32 uncopied_bytes;
    28  
    29          acpi_status status;
    30  
    31          if (!(*ppos)) {
    32                  /* parse the table header to get the table length */
    33                  if (count <= sizeof(struct acpi_table_header))
    34                          return -EINVAL;
  > 35                  if (get_user(max_size,
    36                                  &(struct acpi_table_header 
*)user_buf->length))
    37                          return -EFAULT;
    38                  uncopied_bytes = max_size;
    39                  buf = kzalloc(max_size, GFP_KERNEL);
    40                  if (!buf)
    41                          return -ENOMEM;
    42          }
    43  
    44          if (buf == NULL)
    45                  return -EINVAL;
    46  
    47          if ((*ppos > max_size) ||
    48              (*ppos + count > max_size) ||
    49              (*ppos + count < count) ||
    50              (count > uncopied_bytes))
    51                  return -EINVAL;
    52  
    53          if (copy_from_user(buf + (*ppos), user_buf, count)) {
    54                  kfree(buf);
    55                  buf = NULL;
    56                  return -EFAULT;
    57          }
    58          /* Ensure table length is not changed in the second copy */
    59          (struct acpi_table_header *)(buf + (*ppos))->length = max_size;
    60  
    61          uncopied_bytes -= count;
    62          *ppos += count;
    63  
    64          if (!uncopied_bytes) {
    65                  status = acpi_install_method(buf);
    66                  kfree(buf);
    67                  buf = NULL;
    68                  if (ACPI_FAILURE(status))
    69                          return -EINVAL;
    70                  add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, 
LOCKDEP_NOW_UNRELIABLE);
    71          }
    72  
    73          return count;
    74  }
    75  

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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