Re: arch/riscv/kernel/traps.c:48 die() warn: variable dereferenced before check 'regs' (see line 46)

[Xianting Tian]

在 2022/9/21 上午4:06, Palmer Dabbelt 写道:
> On Thu, 11 Aug 2022 03:42:28 PDT (-0700), 
> xianting.tian@xxxxxxxxxxxxxxxxx wrote:
> > 在 2022/8/11 下午6:33, Dan Carpenter 写道:
> > > tree: 
> > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
> > > master
> > > head:   f41445645ab5d172e6090d00c332c335d8dba337
> > > commit: 3f1901110a89b0e2e13adb2ac8d1a7102879ea98 RISC-V: Add fast 
> > > call path of crash_kexec()
> > > config: riscv-randconfig-m031-20220810 
> > > (https://download.01.org/0day-ci/archive/20220811/202208110538.uaLOQmBs-lkp@xxxxxxxxx/config)
> > > compiler: riscv64-linux-gcc (GCC) 12.1.0
> > >
> > > If you fix the issue, kindly add following tag where applicable
> > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > >
> > > smatch warnings:
> > > arch/riscv/kernel/traps.c:48 die() warn: variable dereferenced 
> > > before check 'regs' (see line 46)
> > >
> > > vim +/regs +48 arch/riscv/kernel/traps.c
> > >
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  31  void die(struct 
> > > pt_regs *regs, const char *str)
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  32  {
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  33      static int 
> > > die_counter;
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  34      int ret;
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  35
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  36 oops_enter();
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  37
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  38 
> > > spin_lock_irq(&die_lock);
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  39 console_verbose();
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  40 bust_spinlocks(1);
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  41
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  42 pr_emerg("%s 
> > > [#%d]\n", str, ++die_counter);
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  43 print_modules();
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  44 show_regs(regs);
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  45
> > > a4c3733d32a72f Christoph Hellwig 2019-10-28 @46      ret = 
> > > notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
> > > ^^^^^^^^^^^
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  47
> > > 3f1901110a89b0 Xianting Tian     2022-06-06 @48      if (regs && 
> > > kexec_should_crash(current))
> > > ^^^^
> > >
> > > Delete this NULL check.
> > thanks,  I will send another fixup patch to fix the issue, is it OK?
>
> You're always welcome to send fixes, but I didn't see anything so I 
> just sent along 
> https://lore.kernel.org/r/20220920200037.6727-1-palmer@xxxxxxxxxxxx/
Thanks Palmer for the fix :)
> > > 3f1901110a89b0 Xianting Tian     2022-06-06  49 crash_kexec(regs);
> > > 3f1901110a89b0 Xianting Tian     2022-06-06  50
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  51 bust_spinlocks(0);
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  52 add_taint(TAINT_DIE, 
> > > LOCKDEP_NOW_UNRELIABLE);
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  53 
> > > spin_unlock_irq(&die_lock);
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  54 oops_exit();
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  55
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  56      if 
> > > (in_interrupt())
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  57 panic("Fatal 
> > > exception in interrupt");
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  58      if (panic_on_oops)
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  59 panic("Fatal 
> > > exception");
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  60      if (ret != 
> > > NOTIFY_STOP)
> > > 0e25498f8cd43c Eric W. Biederman 2021-06-28  61 
> > > make_task_dead(SIGSEGV);
> > > 76d2a0493a17d4 Palmer Dabbelt    2017-07-10  62  }