iov_iter_extract_pages() doesn't correctly handle skipping over initial zero-length entries in ITER_KVEC and ITER_BVEC-type iterators. The problem is that it accidentally reduces maxsize to 0 when it skipping and thus runs to the end of the array and returns 0.
Fix this by sticking the calculated size-to-copy in a new variable rather than back in maxsize.
Fixes: 7d58fe731028 ("iov_iter: Add a function to extract a page list from an iterator") Signed-off-by: David Howells dhowells@redhat.com cc: Christoph Hellwig hch@lst.de cc: Christian Brauner brauner@kernel.org cc: Jens Axboe axboe@kernel.dk cc: Al Viro viro@zeniv.linux.org.uk cc: David Hildenbrand david@redhat.com cc: John Hubbard jhubbard@nvidia.com cc: linux-mm@kvack.org cc: linux-block@vger.kernel.org cc: linux-fsdevel@vger.kernel.org --- lib/iov_iter.c | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-)
diff --git a/lib/iov_iter.c b/lib/iov_iter.c index b31597b0ca20..27234a820eeb 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1654,14 +1654,14 @@ static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i, size_t *offset0) { struct page **p, *page; - size_t skip = i->iov_offset, offset; + size_t skip = i->iov_offset, offset, size; int k;
for (;;) { if (i->nr_segs == 0) return 0; - maxsize = min(maxsize, i->bvec->bv_len - skip); - if (maxsize) + size = min(maxsize, i->bvec->bv_len - skip); + if (size) break; i->iov_offset = 0; i->nr_segs--; @@ -1674,16 +1674,16 @@ static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i, offset = skip % PAGE_SIZE; *offset0 = offset;
- maxpages = want_pages_array(pages, maxsize, offset, maxpages); + maxpages = want_pages_array(pages, size, offset, maxpages); if (!maxpages) return -ENOMEM; p = *pages; for (k = 0; k < maxpages; k++) p[k] = page + k;
- maxsize = min_t(size_t, maxsize, maxpages * PAGE_SIZE - offset); - iov_iter_advance(i, maxsize); - return maxsize; + size = min_t(size_t, size, maxpages * PAGE_SIZE - offset); + iov_iter_advance(i, size); + return size; }
/* @@ -1698,14 +1698,14 @@ static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i, { struct page **p, *page; const void *kaddr; - size_t skip = i->iov_offset, offset, len; + size_t skip = i->iov_offset, offset, len, size; int k;
for (;;) { if (i->nr_segs == 0) return 0; - maxsize = min(maxsize, i->kvec->iov_len - skip); - if (maxsize) + size = min(maxsize, i->kvec->iov_len - skip); + if (size) break; i->iov_offset = 0; i->nr_segs--; @@ -1717,13 +1717,13 @@ static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i, offset = (unsigned long)kaddr & ~PAGE_MASK; *offset0 = offset;
- maxpages = want_pages_array(pages, maxsize, offset, maxpages); + maxpages = want_pages_array(pages, size, offset, maxpages); if (!maxpages) return -ENOMEM; p = *pages;
kaddr -= offset; - len = offset + maxsize; + len = offset + size; for (k = 0; k < maxpages; k++) { size_t seg = min_t(size_t, len, PAGE_SIZE);
@@ -1737,9 +1737,9 @@ static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i, kaddr += PAGE_SIZE; }
- maxsize = min_t(size_t, maxsize, maxpages * PAGE_SIZE - offset); - iov_iter_advance(i, maxsize); - return maxsize; + size = min_t(size_t, size, maxpages * PAGE_SIZE - offset); + iov_iter_advance(i, size); + return size; }
/*