fs, elf: make sure to page align bss in load_elf_library

commit 24962af7e1041b7e50c1bc71d8d10dc678c556b5 upstream.

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 73b01e474fdc630bcc71e6c883d59b5009b64502..c0e3f91e28e91ed128d9b2285999a9bfd5dee05c 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1235,9 +1235,8 @@ static int load_elf_library(struct file *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)