linux-kernel - [PATCH] fs, elf: Make sure to page align bss in load_elf

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Message-Id: <20180705145539.9627-1-osalvador@techadventures.net>
Date:   Thu,  5 Jul 2018 16:55:39 +0200
From:   osalvador@...hadventures.net
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, mhocko@...e.com,
        penguin-kernel@...ove.sakura.ne.jp, keescook@...omium.org,
        nicolas.pitre@...aro.org, Oscar Salvador <osalvador@...e.de>
Subject: [PATCH] fs, elf: Make sure to page align bss in load_elf_library

From: Oscar Salvador <osalvador@...e.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@...e.de>
Tested-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Reported-by: syzbot+5dcb560fe12aa5091c06@...kaller.appspotmail.com
---
 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