linux-kernel - [PATCH 4.9 21/32] fs, elf: make sure to page align bss in load_elf

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Message-Id: <20180716073507.187864821@linuxfoundation.org>
Date:   Mon, 16 Jul 2018 09:36:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Oscar Salvador <osalvador@...e.de>,
        syzbot+5dcb560fe12aa5091c06@...kaller.appspotmail.com,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...e.com>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.9 21/32] fs, elf: make sure to page align bss in load_elf_library

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Oscar Salvador <osalvador@...e.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@...e.de>
Reported-by: syzbot+5dcb560fe12aa5091c06@...kaller.appspotmail.com
Tested-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Acked-by: Kees Cook <keescook@...omium.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Nicolas Pitre <nicolas.pitre@...aro.org>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/binfmt_elf.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1217,9 +1217,8 @@ 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 (error)