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

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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
5c64097aa0, 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>
This commit is contained in:
J. Bruce Fields 2007-03-21 08:50:12 +11:00 committed by Herbert Xu
parent 5851fadce8
commit f70ee5ec8f
1 changed files with 2 additions and 2 deletions
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4
crypto/scatterwalk.c
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@ -91,6 +91,8 @@ void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
memcpy_dir(buf, vaddr, len_this_page, out);
scatterwalk_unmap(vaddr, out);
scatterwalk_advance(walk, nbytes);
if (nbytes == len_this_page)
break;
@ -99,7 +101,5 @@ void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
scatterwalk_pagedone(walk, out, 1);
}
scatterwalk_advance(walk, nbytes);
}
EXPORT_SYMBOL_GPL(scatterwalk_copychunks);