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fuse: honour max_read and max_write in direct_io mode 

The third argument of fuse_get_user_pages() "nbytesp" refers to the number of
bytes a caller asked to pack into fuse request. This value may be lesser
than capacity of fuse request or iov_iter.  So fuse_get_user_pages() must
ensure that *nbytesp won't grow.

Now, when helper iov_iter_get_pages() performs all hard work of extracting
pages from iov_iter, it can be done by passing properly calculated
"maxsize" to the helper.

The other caller of iov_iter_get_pages() (dio_refill_pages()) doesn't need
this capability, so pass LONG_MAX as the maxsize argument here.

Fixes: c9c37e2e63 ("fuse: switch to iov_iter_get_pages()")
Reported-by: Werner Baumann <werner.baumann@onlinehome.de>
Tested-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Miklos Szeredi 2014-09-24 17:09:11 +02:00 committed by Al Viro
parent b928095b0a
commit 2c80929c4c
4 changed files with 12 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/direct-io.c
View File

@ -158,7 +158,7 @@ static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
{
ssize_t ret;
ret = iov_iter_get_pages(sdio->iter, dio->pages, DIO_PAGES,
ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,
&sdio->from);
if (ret < 0 && sdio->blocks_available && (dio->rw & WRITE)) {

1
fs/fuse/file.c
View File

@ -1305,6 +1305,7 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
size_t start;
ssize_t ret = iov_iter_get_pages(ii,
&req->pages[req->num_pages],
*nbytesp - nbytes,
req->max_pages - req->num_pages,
&start);
if (ret < 0)

2
include/linux/uio.h
View File

@ -84,7 +84,7 @@ unsigned long iov_iter_alignment(const struct iov_iter *i);
void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
unsigned long nr_segs, size_t count);
ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
unsigned maxpages, size_t *start);
size_t maxsize, unsigned maxpages, size_t *start);
ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
size_t maxsize, size_t *start);
int iov_iter_npages(const struct iov_iter *i, int maxpages);

14
mm/iov_iter.c
View File

@ -310,7 +310,7 @@ void iov_iter_init(struct iov_iter *i, int direction,
EXPORT_SYMBOL(iov_iter_init);
static ssize_t get_pages_iovec(struct iov_iter *i,
struct page **pages, unsigned maxpages,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
{
size_t offset = i->iov_offset;
@ -323,6 +323,8 @@ static ssize_t get_pages_iovec(struct iov_iter *i,
len = iov->iov_len - offset;
if (len > i->count)
len = i->count;
if (len > maxsize)
len = maxsize;
addr = (unsigned long)iov->iov_base + offset;
len += *start = addr & (PAGE_SIZE - 1);
if (len > maxpages * PAGE_SIZE)
@ -588,13 +590,15 @@ static unsigned long alignment_bvec(const struct iov_iter *i)
}
static ssize_t get_pages_bvec(struct iov_iter *i,
struct page **pages, unsigned maxpages,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
{
const struct bio_vec *bvec = i->bvec;
size_t len = bvec->bv_len - i->iov_offset;
if (len > i->count)
len = i->count;
if (len > maxsize)
len = maxsize;
/* can't be more than PAGE_SIZE */
*start = bvec->bv_offset + i->iov_offset;
@ -711,13 +715,13 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
EXPORT_SYMBOL(iov_iter_alignment);
ssize_t iov_iter_get_pages(struct iov_iter *i,
struct page **pages, unsigned maxpages,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
{
if (i->type & ITER_BVEC)
return get_pages_bvec(i, pages, maxpages, start);
return get_pages_bvec(i, pages, maxsize, maxpages, start);
else
return get_pages_iovec(i, pages, maxpages, start);
return get_pages_iovec(i, pages, maxsize, maxpages, start);
}
EXPORT_SYMBOL(iov_iter_get_pages);