Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 21 Nov 2011 16:49:07 -0800 | Subject | Re: [PATCH] eCryptfs: Check array bounds for filename characters |
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On Mon, Nov 21, 2011 at 3:32 PM, Michael Halcrow <mhalcrow@google.com> wrote: > Characters with ASCII values greater than the size of > filename_rev_map[] are valid filename > characters. ecryptfs_decode_from_filename() will access kernel memory > beyond that array, and ecryptfs_parse_tag_70_packet() will then > decrypt those characters.
Ugh. I really don't like the patch.
Why isn't the patch just this one-liner:
diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c index 58609bde3b9f..7c50715c05d6 100644 --- a/fs/ecryptfs/crypto.c +++ b/fs/ecryptfs/crypto.c @@ -1943,7 +1943,7 @@ static unsigned char *portable_filename_chars = ("-.0123456789ABCD"
/* We could either offset on every reverse map or just pad some 0x00's * at the front here */ -static const unsigned char filename_rev_map[] = { +static const unsigned char filename_rev_map[256] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 7 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 15 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 23 */
instead?
Making invalid characters over \x50 be somehow magically different from invalid characters elsewhere seems just totally bogus. There are lots of characters that aren't valid, and they have the filename_rev_map[] value of 0 elsewhere.
So the simpler one-liner is not only simpler, but gives much saner semantics, I think - now invalid character '\x05' gets exactly the same result as invalid character '\xf5'.
Hmm?
Linus
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