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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Michal Hocko" <mhocko@suse.com>,
        "Oscar Salvador" <osalvador@suse.de>,
        "Nicolas Pitre" <nicolas.pitre@linaro.org>,
        "Linus Torvalds" <torvalds@linux-foundation.org>,
        syzbot+5dcb560fe12aa5091c06@syzkaller.appspotmail.com,
        "Kees Cook" <keescook@chromium.org>,
        "Tetsuo Handa" <penguin-kernel@i-love.sakura.ne.jp>
Date:   Sun, 11 Nov 2018 19:49:05 +0000
Message-ID: <lsq.1541965745.337815760@decadent.org.uk>
Subject: [PATCH 3.16 253/366] fs, elf: make sure to page align bss in
 load_elf_library
In-Reply-To: <lsq.1541965744.387173642@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Oscar Salvador <osalvador@suse.de>

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 fs/binfmt_elf.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1083,9 +1083,8 @@ 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 (BAD_ADDR(error))