Re: [PATCH] binfmt_elf: Support segments with 0 filesz and misaligned starts
From: Dan Carpenter
Date: Tue Sep 26 2023 - 09:50:06 EST
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@xxxxxxxxx/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230926/202309261925.QvgPAYL7-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>
| Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
| Closes: https://lore.kernel.org/r/202309261925.QvgPAYL7-lkp@xxxxxxxxx/
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 }
--
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