From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 In-Reply-To: <20180706071323.GA7959@techadventures.net> References: <20180705145539.9627-1-osalvador@techadventures.net> <20180706071323.GA7959@techadventures.net> From: Kees Cook Date: Fri, 6 Jul 2018 12:23:38 -0700 Message-ID: Subject: Re: [PATCH] fs, elf: Make sure to page align bss in load_elf_library To: Oscar Salvador Cc: "linux-fsdevel@vger.kernel.org" , Linux-MM , LKML , Michal Hocko , Tetsuo Handa , Nicolas Pitre , Oscar Salvador , Andrew Morton Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: On Fri, Jul 6, 2018 at 12:13 AM, Oscar Salvador wrote: > On Thu, Jul 05, 2018 at 08:44:18AM -0700, Kees Cook wrote: >> On Thu, Jul 5, 2018 at 7:55 AM, wrote: >> > From: Oscar Salvador >> > >> > 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 >> > Tested-by: Tetsuo Handa >> > 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 >> >> -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 >> > > CC Andrew > > Hi Andrew, > > in case this patch gets accepted, does it have to go through your tree? > Or is it for someone else to take it? (FWIW, binfmt_elf changes have traditionally gone through -mm, yes.) -Kees -- Kees Cook Pixel Security