Re: [PATCH] x86/xen: Fix some null pointer dereference issues in smp.c

[kernel test robot <lkp@xxxxxxxxx>]

Hi Kunwu,

kernel test robot noticed the following build warnings:

[auto build test WARNING on tip/x86/core]
[also build test WARNING on linus/master v6.7 next-20240112]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    
https://github.com/intel-lab-lkp/linux/commits/Kunwu-Chan/x86-xen-Fix-some-null-pointer-dereference-issues-in-smp-c/20240115-180429
base:   tip/x86/core
patch link:    
https://lore.kernel.org/r/20240115100138.34340-1-chentao%40kylinos.cn
patch subject: [PATCH] x86/xen: Fix some null pointer dereference issues in 
smp.c
config: x86_64-rhel-8.3-rust 
(https://download.01.org/0day-ci/archive/20240116/202401161119.iof6BQsf-lkp@xxxxxxxxx/config)
compiler: ClangBuiltLinux clang version 17.0.6 
(https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): 
(https://download.01.org/0day-ci/archive/20240116/202401161119.iof6BQsf-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: 
https://lore.kernel.org/oe-kbuild-all/202401161119.iof6BQsf-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

>> arch/x86/xen/smp.c:68:6: warning: variable 'rc' is used uninitialized 
>> whenever 'if' condition is true [-Wsometimes-uninitialized]
      68 |         if (!resched_name)
         |             ^~~~~~~~~~~~~
   arch/x86/xen/smp.c:127:9: note: uninitialized use occurs here
     127 |         return rc;
         |                ^~
   arch/x86/xen/smp.c:68:2: note: remove the 'if' if its condition is always 
false
      68 |         if (!resched_name)
         |         ^~~~~~~~~~~~~~~~~~
      69 |                 goto fail;
         |                 ~~~~~~~~~
   arch/x86/xen/smp.c:64:8: note: initialize the variable 'rc' to silence this 
warning
      64 |         int rc;
         |               ^
         |                = 0
   1 warning generated.


vim +68 arch/x86/xen/smp.c

    61  
    62  int xen_smp_intr_init(unsigned int cpu)
    63  {
    64          int rc;
    65          char *resched_name, *callfunc_name, *debug_name;
    66  
    67          resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
  > 68          if (!resched_name)
    69                  goto fail;
    70          per_cpu(xen_resched_irq, cpu).name = resched_name;
    71          rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
    72                                      cpu,
    73                                      xen_reschedule_interrupt,
    74                                      IRQF_PERCPU|IRQF_NOBALANCING,
    75                                      resched_name,
    76                                      NULL);
    77          if (rc < 0)
    78                  goto fail;
    79          per_cpu(xen_resched_irq, cpu).irq = rc;
    80  
    81          callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
    82          if (!callfunc_name)
    83                  goto fail;
    84          per_cpu(xen_callfunc_irq, cpu).name = callfunc_name;
    85          rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
    86                                      cpu,
    87                                      xen_call_function_interrupt,
    88                                      IRQF_PERCPU|IRQF_NOBALANCING,
    89                                      callfunc_name,
    90                                      NULL);
    91          if (rc < 0)
    92                  goto fail;
    93          per_cpu(xen_callfunc_irq, cpu).irq = rc;
    94  
    95          if (!xen_fifo_events) {
    96                  debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
    97                  if (!debug_name)
    98                          goto fail;
    99                  per_cpu(xen_debug_irq, cpu).name = debug_name;
   100                  rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu,
   101                                               xen_debug_interrupt,
   102                                               IRQF_PERCPU | 
IRQF_NOBALANCING,
   103                                               debug_name, NULL);
   104                  if (rc < 0)
   105                          goto fail;
   106                  per_cpu(xen_debug_irq, cpu).irq = rc;
   107          }
   108  
   109          callfunc_name = kasprintf(GFP_KERNEL, "callfuncsingle%d", cpu);
   110          if (!callfunc_name)
   111                  goto fail;
   112          per_cpu(xen_callfuncsingle_irq, cpu).name = callfunc_name;
   113          rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_SINGLE_VECTOR,
   114                                      cpu,
   115                                      xen_call_function_single_interrupt,
   116                                      IRQF_PERCPU|IRQF_NOBALANCING,
   117                                      callfunc_name,
   118                                      NULL);
   119          if (rc < 0)
   120                  goto fail;
   121          per_cpu(xen_callfuncsingle_irq, cpu).irq = rc;
   122  
   123          return 0;
   124  
   125   fail:
   126          xen_smp_intr_free(cpu);
   127          return rc;
   128  }
   129  

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