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From: kernel test robot <lkp@intel.com>
To: "Vladimir Kondratiev" <vladimir.kondratiev@mobileye.com>,
	"Paul Walmsley" <pjw@kernel.org>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Masami Hiramatsu" <mhiramat@kernel.org>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Guo Ren" <guoren@kernel.org>,
	"Pekka Enberg" <penberg@kernel.org>,
	"Patrick Stählin" <me@packi.ch>
Cc: oe-kbuild-all@lists.linux.dev, linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	Vladimir Kondratiev <vladimir.kondratiev@mobileye.com>
Subject: Re: [PATCH v4 2/3] riscv: probes: reject probes inside an LR/SC sequence
Date: Mon, 16 Nov 2026 04:12:52 +0800	[thread overview]
Message-ID: <202611160417.wVX1is4j-lkp@intel.com> (raw)
In-Reply-To: <20261115-probes-in-lrsc-v4-2-48b9b036bd1d@mobileye.com>

Hi Vladimir,

kernel test robot noticed the following build warnings:

[auto build test WARNING on c03c1a14507dfaf8b856c2608f9ac216021fc222]

url:    https://github.com/intel-lab-lkp/linux/commits/Vladimir-Kondratiev/riscv-kprobes-fix-out-of-bounds-read-in-riscv_probe_decode_insn/20261115-143733
base:   c03c1a14507dfaf8b856c2608f9ac216021fc222
patch link:    https://lore.kernel.org/r/20261115-probes-in-lrsc-v4-2-48b9b036bd1d%40mobileye.com
patch subject: [PATCH v4 2/3] riscv: probes: reject probes inside an LR/SC sequence
config: riscv-randconfig-1000-20261116 (https://download.01.org/0day-ci/archive/20261116/202611160417.wVX1is4j-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 15.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261116/202611160417.wVX1is4j-lkp@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202611160417.wVX1is4j-lkp@intel.com/

All warnings (new ones prefixed by >>):

   arch/riscv/kernel/probes/kprobes.c: In function 'arch_check_kprobe':
>> arch/riscv/kernel/probes/kprobes.c:72:20: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
      72 |                 if (tmp == addr)
         |                    ^


vim +/else +72 arch/riscv/kernel/probes/kprobes.c

c22b0bcb1dd024 Guo Ren             2020-12-17  51  
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  52  /*
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  53   * Walk the instructions from the enclosing symbol up to addr to check that
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  54   * addr is an instruction boundary. Then reject a probe inside an LR/SC
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  55   * sequence: the breakpoint trap drops the reservation, so the SC would fail
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  56   * and the loop would hit the probe again on every retry. The sequence is
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  57   * recognised by a forward scan with the constrained-sequence rules, as for
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  58   * uprobes, so an lr that is not followed by an sc (as in __cmpwait()) does
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  59   * not taint the rest of the function.
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  60   */
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  61  static int __kprobes arch_check_kprobe(unsigned long addr)
87f48c7ccc73af Guo Ren             2023-01-31  62  {
9e68bd803fac49 Fabian Vogt         2025-09-10  63  	unsigned long tmp, offset;
9e68bd803fac49 Fabian Vogt         2025-09-10  64  
9e68bd803fac49 Fabian Vogt         2025-09-10  65  	/* start iterating at the closest preceding symbol */
9e68bd803fac49 Fabian Vogt         2025-09-10  66  	if (!kallsyms_lookup_size_offset(addr, NULL, &offset))
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  67  		return -EILSEQ;
9e68bd803fac49 Fabian Vogt         2025-09-10  68  
9e68bd803fac49 Fabian Vogt         2025-09-10  69  	tmp = addr - offset;
87f48c7ccc73af Guo Ren             2023-01-31  70  
87f48c7ccc73af Guo Ren             2023-01-31  71  	while (tmp <= addr) {
87f48c7ccc73af Guo Ren             2023-01-31 @72  		if (tmp == addr)
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  73  			if (riscv_probe_in_lrsc_body((u16 *)addr, RISCV_LRSC_SCAN_BYTES))
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  74  				return -EINVAL;
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  75  			else
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  76  				return 0;
87f48c7ccc73af Guo Ren             2023-01-31  77  
87f48c7ccc73af Guo Ren             2023-01-31  78  		tmp += GET_INSN_LENGTH(*(u16 *)tmp);
87f48c7ccc73af Guo Ren             2023-01-31  79  	}
87f48c7ccc73af Guo Ren             2023-01-31  80  
c0b7e72c7a4b06 Vladimir Kondratiev 2026-11-15  81  	return -EILSEQ;
87f48c7ccc73af Guo Ren             2023-01-31  82  }
87f48c7ccc73af Guo Ren             2023-01-31  83  

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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  parent reply	other threads:[~2026-11-15 20:14 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-15 12:37 [PATCH v4 0/3] riscv: probes: reject probes inside an LR/SC sequence Vladimir Kondratiev
2026-11-15 12:37 ` [PATCH v4 1/3] riscv: kprobes: fix out-of-bounds read in riscv_probe_decode_insn Vladimir Kondratiev
2026-11-15 12:37 ` [PATCH v4 2/3] riscv: probes: reject probes inside an LR/SC sequence Vladimir Kondratiev
2026-11-15 18:37   ` kernel test robot
2026-11-15 20:12   ` kernel test robot [this message]
2026-11-15 12:37 ` [PATCH v4 3/3] riscv: kprobes: add KUnit test for LR/SC sequence rejection Vladimir Kondratiev

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