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Commit dd111be6 authored by Jann Horn's avatar Jann Horn Committed by Linus Torvalds
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swapfile: fix memory corruption via malformed swapfile 

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: default avatarJann Horn <jann@thejh.net>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarJerome Marchand <jmarchan@redhat.com>
Acked-by: default avatarJohannes 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>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6b36ba59

mm/swapfile.c

+2 −0
Original line number Diff line number Diff line
@@ -2224,6 +2224,8 @@ 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]);

	}