From: J. Bruce Fields 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: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f70ee5ec8fc59ba2d905e6daf0d395edf6fb461d;p=linux-2.6 [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" Signed-off-by: Herbert Xu --- diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c index 35172d3f04..a664231217 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);