From: Oscar Salvador osalvador@suse.de Subject: fs, elf: make sure to page align bss in load_elf_library

The current code does not make sure to page align bss before calling vm_brk(), and this can lead to a VM_BUG_ON() in __mm_populate() due to the requested lenght not being correctly aligned.

Let us make sure to align it properly.

Kees: only applicable to CONFIG_USELIB kernels: 32-bit and configured for libc5.

Link: http://lkml.kernel.org/r/20180705145539.9627-1-osalvador@techadventures.net Signed-off-by: Oscar Salvador osalvador@suse.de Reported-by: syzbot+5dcb560fe12aa5091c06@syzkaller.appspotmail.com Tested-by: Tetsuo Handa penguin-kernel@i-love.sakura.ne.jp Acked-by: Kees Cook keescook@chromium.org Cc: Michal Hocko mhocko@suse.com Cc: Nicolas Pitre nicolas.pitre@linaro.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/binfmt_elf.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)

diff -puN fs/binfmt_elf.c~fs-elf-make-sure-to-page-align-bss-in-load_elf_library fs/binfmt_elf.c --- a/fs/binfmt_elf.c~fs-elf-make-sure-to-page-align-bss-in-load_elf_library +++ a/fs/binfmt_elf.c @@ -1259,9 +1259,8 @@ static int load_elf_library(struct file goto out_free_ph; }

- len = ELF_PAGESTART(eppnt->p_filesz + eppnt->p_vaddr + - ELF_MIN_ALIGN - 1); - bss = eppnt->p_memsz + eppnt->p_vaddr; + len = ELF_PAGEALIGN(eppnt->p_filesz + eppnt->p_vaddr); + bss = ELF_PAGEALIGN(eppnt->p_memsz + eppnt->p_vaddr); if (bss > len) { error = vm_brk(len, bss - len); if (error) _