From 4f43178d453f8707f412b2721703b36f53484901 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Thu, 10 Nov 2016 10:46:19 -0800 Subject: [PATCH] swapfile: fix memory corruption via malformed swapfile 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 Acked-by: Kees Cook Acked-by: Jerome Marchand Acked-by: Johannes Weiner Cc: "Kirill A. Shutemov" Cc: Vlastimil Babka Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Willy Tarreau --- mm/swapfile.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/swapfile.c b/mm/swapfile.c index bd3829540676..71063e20beb7 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1988,6 +1988,8 @@ static unsigned long read_swap_header(struct swap_info_struct *p, 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]); }