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: c9c37e2e6378 ("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>

diff --git a/fs/direct-io.c b/fs/direct-io.c
index c311640..e181b6b 100644 (file)
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -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)) {

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 912061a..caa8d95 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -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)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 48d64e6..290fbf0 100644 (file)
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -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);

diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index ab88dc0..9a09f20 100644 (file)
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -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);