linux-kernel - [PATCH 20/52] Limit number of pages returned by direct

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Date:   Mon, 10 Dec 2018 12:12:46 -0500
From:   Vivek Goyal <vgoyal@...hat.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     vgoyal@...hat.com, miklos@...redi.hu, stefanha@...hat.com,
        dgilbert@...hat.com, sweil@...hat.com, swhiteho@...hat.com
Subject: [PATCH 20/52] Limit number of pages returned by direct_access()

Truncate number of pages mapped by direct_access() to remain with-in window
size. User might request mapping pages beyond window size.

Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
---
 fs/fuse/virtio_fs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index e4d5e0cd41ba..ef1469b38a6d 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -449,13 +449,14 @@ static long virtio_fs_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
 {
 	struct virtio_fs *fs = dax_get_private(dax_dev);
 	phys_addr_t offset = PFN_PHYS(pgoff);
+	size_t max_nr_pages = fs->window_len/PAGE_SIZE - pgoff;
 
 	if (kaddr)
 		*kaddr = fs->window_kaddr + offset;
 	if (pfn)
 		*pfn = phys_to_pfn_t(fs->window_phys_addr + offset,
 					PFN_DEV | PFN_MAP);
-	return nr_pages;
+	return nr_pages > max_nr_pages ? max_nr_pages : nr_pages;
 }
 
 static size_t virtio_fs_copy_from_iter(struct dax_device *dax_dev,
-- 
2.13.6