[PATCH] fs: Fix page_mkwrite off-by-one errors

[Andreas Gruenbacher]

Fix a check in block_page_mkwrite meant to determine whether an offset
is within the inode size.  This error has spread to several filesystems
and to iomap_page_mkwrite, so fix those instances as well.

Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>

---

This patch has a trivial conflict with commit "iomap: Fix overflow in
iomap_page_mkwrite" in Darrick's iomap pull request for 5.5:

  20191125190907.GN6219@magnolia/">https://lore.kernel.org/lkml/20191125190907.GN6219@magnolia/
---
 fs/buffer.c            | 2 +-
 fs/ceph/addr.c         | 2 +-
 fs/ext4/inode.c        | 2 +-
 fs/f2fs/file.c         | 2 +-
 fs/iomap/buffered-io.c | 2 +-
 fs/ubifs/file.c        | 2 +-
 6 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 86a38b979323..152d391858d4 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2465,7 +2465,7 @@ int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 	lock_page(page);
 	size = i_size_read(inode);
 	if ((page->mapping != inode->i_mapping) ||
-	    (page_offset(page) > size)) {
+	    (page_offset(page) >= size)) {
 		/* We overload EFAULT to mean page got truncated */
 		ret = -EFAULT;
 		goto out_unlock;
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 7ab616601141..9fa0729ece41 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -1575,7 +1575,7 @@ static vm_fault_t ceph_page_mkwrite(struct vm_fault *vmf)
 	do {
 		lock_page(page);
 
-		if ((off > size) || (page->mapping != inode->i_mapping)) {
+		if ((off >= size) || (page->mapping != inode->i_mapping)) {
 			unlock_page(page);
 			ret = VM_FAULT_NOPAGE;
 			break;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 516faa280ced..6dd4efe2fb63 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -6224,7 +6224,7 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
 	lock_page(page);
 	size = i_size_read(inode);
 	/* Page got truncated from under us? */
-	if (page->mapping != mapping || page_offset(page) > size) {
+	if (page->mapping != mapping || page_offset(page) >= size) {
 		unlock_page(page);
 		ret = VM_FAULT_NOPAGE;
 		goto out;
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 29bc0a542759..3436be01af45 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -71,7 +71,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	down_read(&F2FS_I(inode)->i_mmap_sem);
 	lock_page(page);
 	if (unlikely(page->mapping != inode->i_mapping ||
-			page_offset(page) > i_size_read(inode) ||
+			page_offset(page) >= i_size_read(inode) ||
 			!PageUptodate(page))) {
 		unlock_page(page);
 		err = -EFAULT;
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index e25901ae3ff4..d454dbab5133 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1041,7 +1041,7 @@ vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
 	lock_page(page);
 	size = i_size_read(inode);
 	if ((page->mapping != inode->i_mapping) ||
-	    (page_offset(page) > size)) {
+	    (page_offset(page) >= size)) {
 		/* We overload EFAULT to mean page got truncated */
 		ret = -EFAULT;
 		goto out_unlock;
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index cd52585c8f4f..ca0148ec77e6 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1564,7 +1564,7 @@ static vm_fault_t ubifs_vm_page_mkwrite(struct vm_fault *vmf)
 
 	lock_page(page);
 	if (unlikely(page->mapping != inode->i_mapping ||
-		     page_offset(page) > i_size_read(inode))) {
+		     page_offset(page) >= i_size_read(inode))) {
 		/* Page got truncated out from underneath us */
 		goto sigbus;
 	}
-- 
2.20.1