From: Kees Cook <keescook@chromium.org>
To: osalvador@techadventures.net
Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Nicolas Pitre <nicolas.pitre@linaro.org>,
Oscar Salvador <osalvador@suse.de>
Subject: Re: [PATCH] fs, elf: Make sure to page align bss in load_elf_library
Date: Thu, 5 Jul 2018 08:44:18 -0700 [thread overview]
Message-ID: <CAGXu5jL4O_qwwAHmW1C8q77Jv1fe_1JCq6iFxC73VySBkvHSQw@mail.gmail.com> (raw)
In-Reply-To: <20180705145539.9627-1-osalvador@techadventures.net>
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
next prev parent reply other threads:[~2018-07-05 15:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-05 14:55 [PATCH] fs, elf: Make sure to page align bss in load_elf_library osalvador
2018-07-05 15:44 ` Kees Cook [this message]
2018-07-06 7:13 ` Oscar Salvador
2018-07-06 19:23 ` Kees Cook
2018-07-06 22:55 ` Andrew Morton
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