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Date:   Tue, 26 Sep 2023 16:49:57 +0300
From:   Dan Carpenter <dan.carpenter@linaro.org>
To:     oe-kbuild@lists.linux.dev,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Sebastian Ott <sebott@redhat.com>
Cc:     lkp@intel.com, oe-kbuild-all@lists.linux.dev,
        Thomas =?iso-8859-1?Q?Wei=DFschuh?= <linux@weissschuh.net>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Mark Brown <broonie@kernel.org>, Willy Tarreau <w@1wt.eu>,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] binfmt_elf: Support segments with 0 filesz and
 misaligned starts
Message-ID: <60c7fdeb-da32-4d21-9e34-368050224d6c@kadam.mountain>
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In-Reply-To: <87jzsemmsd.fsf_-_@email.froward.int.ebiederm.org>
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Hi Eric,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Eric-W-Biederman/binfmt_elf-Support-segments-with-0-filesz-and-misaligned-starts/20230925-210022
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/execve
patch link:    https://lore.kernel.org/r/87jzsemmsd.fsf_-_%40email.froward.int.ebiederm.org
patch subject: [PATCH] binfmt_elf: Support segments with 0 filesz and misaligned starts
config: i386-randconfig-141-20230926 (https://download.01.org/0day-ci/archive/20230926/202309261925.QvgPAYL7-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230926/202309261925.QvgPAYL7-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>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202309261925.QvgPAYL7-lkp@intel.com/

smatch warnings:
fs/binfmt_elf.c:431 elf_load() error: uninitialized symbol 'map_addr'.

vim +/map_addr +431 fs/binfmt_elf.c

a6409120b31666 Eric W. Biederman 2023-09-25  390  static unsigned long elf_load(struct file *filep, unsigned long addr,
a6409120b31666 Eric W. Biederman 2023-09-25  391  		const struct elf_phdr *eppnt, int prot, int type,
a6409120b31666 Eric W. Biederman 2023-09-25  392  		unsigned long total_size)
a6409120b31666 Eric W. Biederman 2023-09-25  393  {
a6409120b31666 Eric W. Biederman 2023-09-25  394  	unsigned long zero_start, zero_end;
a6409120b31666 Eric W. Biederman 2023-09-25  395  	unsigned long map_addr;
a6409120b31666 Eric W. Biederman 2023-09-25  396  
a6409120b31666 Eric W. Biederman 2023-09-25  397  	if (eppnt->p_filesz) {
a6409120b31666 Eric W. Biederman 2023-09-25  398  		map_addr = elf_map(filep, addr, eppnt, prot, type, total_size);
a6409120b31666 Eric W. Biederman 2023-09-25  399  		if (BAD_ADDR(map_addr))
a6409120b31666 Eric W. Biederman 2023-09-25  400  			return map_addr;
a6409120b31666 Eric W. Biederman 2023-09-25  401  		if (eppnt->p_memsz > eppnt->p_filesz) {
a6409120b31666 Eric W. Biederman 2023-09-25  402  			zero_start = map_addr + ELF_PAGEOFFSET(eppnt->p_vaddr) +
a6409120b31666 Eric W. Biederman 2023-09-25  403  				eppnt->p_filesz;
a6409120b31666 Eric W. Biederman 2023-09-25  404  			zero_end = map_addr + ELF_PAGEOFFSET(eppnt->p_vaddr) +
a6409120b31666 Eric W. Biederman 2023-09-25  405  				eppnt->p_memsz;
a6409120b31666 Eric W. Biederman 2023-09-25  406  
a6409120b31666 Eric W. Biederman 2023-09-25  407  			/* Zero the end of the last mapped page */
a6409120b31666 Eric W. Biederman 2023-09-25  408  			padzero(zero_start);
a6409120b31666 Eric W. Biederman 2023-09-25  409  		}
a6409120b31666 Eric W. Biederman 2023-09-25  410  	} else {
a6409120b31666 Eric W. Biederman 2023-09-25  411  		zero_start = ELF_PAGESTART(addr);
a6409120b31666 Eric W. Biederman 2023-09-25  412  		zero_end = zero_start + ELF_PAGEOFFSET(eppnt->p_vaddr) +
a6409120b31666 Eric W. Biederman 2023-09-25  413  			eppnt->p_memsz;

For this else path, map_addr is only set if there is an error.

a6409120b31666 Eric W. Biederman 2023-09-25  414  	}
a6409120b31666 Eric W. Biederman 2023-09-25  415  	if (eppnt->p_memsz > eppnt->p_filesz) {
a6409120b31666 Eric W. Biederman 2023-09-25  416  		/*
a6409120b31666 Eric W. Biederman 2023-09-25  417  		 * Map the last of the segment.
a6409120b31666 Eric W. Biederman 2023-09-25  418  		 * If the header is requesting these pages to be
a6409120b31666 Eric W. Biederman 2023-09-25  419  		 * executable, honour that (ppc32 needs this).
a6409120b31666 Eric W. Biederman 2023-09-25  420  		 */
a6409120b31666 Eric W. Biederman 2023-09-25  421  		int error;
a6409120b31666 Eric W. Biederman 2023-09-25  422  
a6409120b31666 Eric W. Biederman 2023-09-25  423  		zero_start = ELF_PAGEALIGN(zero_start);
a6409120b31666 Eric W. Biederman 2023-09-25  424  		zero_end = ELF_PAGEALIGN(zero_end);
a6409120b31666 Eric W. Biederman 2023-09-25  425  
a6409120b31666 Eric W. Biederman 2023-09-25  426  		error = vm_brk_flags(zero_start, zero_end - zero_start,
a6409120b31666 Eric W. Biederman 2023-09-25  427  				     prot & PROT_EXEC ? VM_EXEC : 0);
a6409120b31666 Eric W. Biederman 2023-09-25  428  		if (error)
a6409120b31666 Eric W. Biederman 2023-09-25  429  			map_addr = error;
a6409120b31666 Eric W. Biederman 2023-09-25  430  	}
a6409120b31666 Eric W. Biederman 2023-09-25 @431  	return map_addr;
a6409120b31666 Eric W. Biederman 2023-09-25  432  }

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