From: J. Bruce Fields <bfields@citi.umich.edu>
Date: Tue, 20 Mar 2007 21:50:12 +0000 (+1100)
Subject: [CRYPTO] api: scatterwalk_copychunks() fails to advance through scatterlist
X-Git-Tag: v2.6.21-rc5~49^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f70ee5ec8fc59ba2d905e6daf0d395edf6fb461d;p=pandora-kernel.git

[CRYPTO] api: scatterwalk_copychunks() fails to advance through scatterlist

In the loop in scatterwalk_copychunks(), if walk->offset is zero,
then scatterwalk_pagedone rounds that up to the nearest page boundary:

		walk->offset += PAGE_SIZE - 1;
		walk->offset &= PAGE_MASK;

which is a no-op in this case, so we don't advance to the next element
of the scatterlist array:

		if (walk->offset >= walk->sg->offset + walk->sg->length)
			scatterwalk_start(walk, sg_next(walk->sg));

and we end up copying the same data twice.

It appears that other callers of scatterwalk_{page}done first advance
walk->offset, so I believe that's the correct thing to do here.

This caused a bug in NFS when run with krb5p security, which would
cause some writes to fail with permissions errors--for example, writes
of less than 8 bytes (the des blocksize) at the start of a file.

A git-bisect shows the bug was originally introduced by
5c64097aa0f6dc4f27718ef47ca9a12538d62860, first in 2.6.19-rc1.

Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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