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authorDavid Howells <dhowells@redhat.com>2023-09-08 17:03:20 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2023-09-09 15:11:49 -0700
commitf741bd7178c95abd7aeac5a9d933ee542f9a5509 (patch)
tree2daa2aee81598fcf690d39ac2424ef90173c00b9
parent6b8bb5b8d9b35fb43f0dbf9fd91b7d35e6232e08 (diff)
iov_iter: Fix iov_iter_extract_pages() with zero-sized entries
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> Reviewed-by: 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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--lib/iov_iter.c30
1 files 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;
}
/*