Messages in this thread Patch in this message | | | From | Jeff Layton <> | Subject | [PATCH] iov_iter: have iov_iter_advance decrement nr_segs appropriately | Date | Mon, 15 Aug 2011 14:07:26 -0400 |
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Currently, when you call iov_iter_advance, then the pointer to the kvec array can be incremented, but it does not decrement the nr_segs value in the iov_iter struct. The result is a iov_iter struct with a nr_segs value that goes beyond the end of the array.
While I'm not aware of anything that's specifically broken by this, it seems odd and a bit dangerous not to decrement that value. If someone were to trust the nr_segs value to be correct, then they could end up walking off the end of the array.
Changing this might also provide some micro-optimization when dealing with the last kvec in an array. Many of the other routines that deal with iov_iter have optimized codepaths when nr_segs == 1.
Cc: Nick Piggin <npiggin@suse.de> Signed-off-by: Jeff Layton <jlayton@redhat.com> --- mm/filemap.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c index 645a080..86508cc 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2113,6 +2113,7 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes) } else { const struct iovec *iov = i->iov; size_t base = i->iov_offset; + unsigned long nr_segs = i->nr_segs; /* * The !iov->iov_len check ensures we skip over unlikely @@ -2128,11 +2129,13 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes) base += copy; if (iov->iov_len == base) { iov++; + nr_segs--; base = 0; } } i->iov = iov; i->iov_offset = base; + i->nr_segs = nr_segs; } } EXPORT_SYMBOL(iov_iter_advance); -- 1.7.6
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