6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Howells <dhowells@xxxxxxxxxx>
commit f741bd7178c95abd7aeac5a9d933ee542f9a5509 upstream.
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@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
lib/iov_iter.c | 30 +++++++++++++++---------------
1 file changed, 15 insertions(+), 15 deletions(-)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1640,14 +1640,14 @@ static ssize_t iov_iter_extract_bvec_pag
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--;
@@ -1660,16 +1660,16 @@ static ssize_t iov_iter_extract_bvec_pag
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;
}
/*
@@ -1684,14 +1684,14 @@ static ssize_t iov_iter_extract_kvec_pag
{
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--;
@@ -1703,13 +1703,13 @@ static ssize_t iov_iter_extract_kvec_pag
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);
@@ -1723,9 +1723,9 @@ static ssize_t iov_iter_extract_kvec_pag
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;
}
/*
