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" <[EMAIL PROTECTED]>
---
crypto/scatterwalk.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
index 35172d3..a664231 100644
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -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);
--
1.5.0.3.31.ge47c
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