------- Comment From mauri...@br.ibm.com 2015-01-26 15:21 EDT------- *** Bug 119945 has been marked as a duplicate of this bug. ***
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to binutils in Ubuntu. https://bugs.launchpad.net/bugs/1412553 Title: RELRO not working on Ubuntu 14.04 Status in binutils package in Ubuntu: Fix Released Status in binutils source package in Trusty: New Bug description: RELRO (RELocation Read-Only) is security feature provided by the linker and implemented in conjunction with glibc to relocations sections that are used to resolve dynamically loaded functions read- only. The GLIBC side looks at the segments placement set by the linker and if they met some criteria regarding alignment, the are mprotect to be read-only. More specifically, on GLIBC code: elf/dl-reloc.c: 324 void internal_function 325 _dl_protect_relro (struct link_map *l) 326 { 327 ElfW(Addr) start = ((l->l_addr + l->l_relro_addr) 328 & ~(GLRO(dl_pagesize) - 1)); 329 ElfW(Addr) end = ((l->l_addr + l->l_relro_addr + l->l_relro_size) 330 & ~(GLRO(dl_pagesize) - 1)); 331 332 if (start != end 333 && __mprotect ((void *) start, end - start, PROT_READ) < 0) 334 { 335 static const char errstring[] = N_("\ 336 cannot apply additional memory protection after relocation"); 337 _dl_signal_error (errno, l->l_name, NULL, errstring); 338 } 339 } The problem is, if linker does not set the alignment correctly, 'start' and 'end' will be equal and thus not protected. And this is happening on Ubuntu 14.04 due the fact its uses default binutils elf{32,64}-ppc.c ELF_COMMONPAGESIZE to align it to 4k instead of 64k. There is a recent patch on binutils-dev maillist [1] to change the default for 64k and Fedora rawhide already sets it [2] in its binutils.spec spec: # On ppc64 and aarch64, we might use 64KiB pages sed -i -e '/#define.*ELF_COMMONPAGESIZE/s/0x1000$/0x10000/' bfd/elf*ppc.c sed -i -e '/#define.*ELF_COMMONPAGESIZE/s/0x1000$/0x10000/' bfd/elf*aarch64.c Ubuntu for powerpc64le should do the same. [1] https://sourceware.org/ml/binutils/2014-12/msg00165.html [2] http://dl.fedoraproject.org/pub/fedora/linux/development/rawhide/source/SRPMS/b/binutils-2.24-29.fc22.src.rpm I tested and building a binutils with the ELF_COMMONPAGESIZE set to 64k instead of default 4k and rebuilding GLIBC I see its relocation sections being correctly mprotected. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/binutils/+bug/1412553/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
