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Message-ID: <20230908160322.1714302-2-dhowells@redhat.com>
Date: Fri, 8 Sep 2023 17:03:20 +0100
From: David Howells <dhowells@...hat.com>
To: Jens Axboe <axboe@...nel.dk>, Al Viro <viro@...iv.linux.org.uk>,
Christoph Hellwig <hch@....de>
Cc: David Howells <dhowells@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Christian Brauner <brauner@...nel.org>,
David Hildenbrand <david@...hat.com>,
John Hubbard <jhubbard@...dia.com>,
Jeff Layton <jlayton@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] iov_iter: Fix iov_iter_extract_pages()
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@...hat.com>
cc: Christoph Hellwig <hch@....de>
cc: Christian Brauner <brauner@...nel.org>
cc: Jens Axboe <axboe@...nel.dk>
cc: Al Viro <viro@...iv.linux.org.uk>
cc: David Hildenbrand <david@...hat.com>
cc: John Hubbard <jhubbard@...dia.com>
cc: linux-mm@...ck.org
cc: linux-block@...r.kernel.org
cc: linux-fsdevel@...r.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;
}
/*
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