• J. Bruce Fields's avatar
    [CRYPTO] api: scatterwalk_copychunks() fails to advance through scatterlist · f70ee5ec
    J. Bruce Fields authored
    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
    5c64097a, first in 2.6.19-rc1.
    Signed-off-by: default avatar"J. Bruce Fields" <bfields@citi.umich.edu>
    Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
scatterwalk.c 2.43 KB