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

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Date:   Thu, 11 Aug 2022 18:42:28 +0800
From:   Xianting Tian <xianting.tian@...ux.alibaba.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>, kbuild@...ts.01.org
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Palmer Dabbelt <palmer@...osinc.com>,
        Guo Ren <guoren@...nel.org>
Subject: Re: arch/riscv/kernel/traps.c:48 die() warn: variable dereferenced
 before check 'regs' (see line 46)


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@intel.com/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@...el.com>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
>
> 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?
>
> 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  }
>