Patch "swapfile: fix memory corruption via malformed swapfile" has been added to the 4.4-stable tree

Patch "swapfile: fix memory corruption via malformed swapfile" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    swapfile: fix memory corruption via malformed swapfile

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     swapfile-fix-memory-corruption-via-malformed-swapfile.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From dd111be69114cc867f8e826284559bfbc1c40e37 Mon Sep 17 00:00:00 2001
From: Jann Horn <jann@thejh.net>
Date: Thu, 10 Nov 2016 10:46:19 -0800
Subject: swapfile: fix memory corruption via malformed swapfile

From: Jann Horn <jann@thejh.net>

commit dd111be69114cc867f8e826284559bfbc1c40e37 upstream.

When root activates a swap partition whose header has the wrong
endianness, nr_badpages elements of badpages are swabbed before
nr_badpages has been checked, leading to a buffer overrun of up to 8GB.

This normally is not a security issue because it can only be exploited
by root (more specifically, a process with CAP_SYS_ADMIN or the ability
to modify a swap file/partition), and such a process can already e.g.
modify swapped-out memory of any other userspace process on the system.

Link: http://lkml.kernel.org/r/1477949533-2509-1-git-send-email-jann@thejh.net
Signed-off-by: Jann Horn <jann@thejh.net>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/swapfile.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2225,6 +2225,8 @@ static unsigned long read_swap_header(st
 		swab32s(&swap_header->info.version);
 		swab32s(&swap_header->info.last_page);
 		swab32s(&swap_header->info.nr_badpages);
+		if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
+			return 0;
 		for (i = 0; i < swap_header->info.nr_badpages; i++)
 			swab32s(&swap_header->info.badpages[i]);
 	}


Patches currently in stable-queue which might be from jann@thejh.net are

queue-4.4/swapfile-fix-memory-corruption-via-malformed-swapfile.patch