Messages in this thread | | | From | Kees Cook <> | Date | Thu, 5 Jul 2018 08:44:18 -0700 | Subject | Re: [PATCH] fs, elf: Make sure to page align bss in load_elf_library |
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On Thu, Jul 5, 2018 at 7:55 AM, <osalvador@techadventures.net> wrote: > From: Oscar Salvador <osalvador@suse.de> > > 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. > > Signed-off-by: Oscar Salvador <osalvador@suse.de> > Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> > Reported-by: syzbot+5dcb560fe12aa5091c06@syzkaller.appspotmail.com
Wow. CONFIG_USELIB? I'm surprised distros are still using this. 32-bit only, and libc5 and earlier only.
Regardless, this appears to match the current bss alignment logic in the main elf loader, so:
Acked-by: Kees Cook <keescook@chromium.org>
-Kees
> --- > fs/binfmt_elf.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index 0ac456b52bdd..816cc921cf36 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -1259,9 +1259,8 @@ 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) > -- > 2.13.6 >
-- Kees Cook Pixel Security
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