fuse: fix reading past EOF

Currently reading a fuse file will stop at cached i_size and return
EOF, even though the file might have grown since the attributes were
last updated.

So detect if trying to read past EOF, and refresh the attributes
before continuing with the read.

Thanks to mpb for the report.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 29 insertions, 19 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 3763757f9fe7..7b3df35cf196 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -775,6 +775,31 @@ static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
 	return err;
 }
 
+int fuse_update_attributes(struct inode *inode, struct kstat *stat,
+			   struct file *file, bool *refreshed)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	int err;
+	bool r;
+
+	if (fi->i_time < get_jiffies_64()) {
+		r = true;
+		err = fuse_do_getattr(inode, stat, file);
+	} else {
+		r = false;
+		err = 0;
+		if (stat) {
+			generic_fillattr(inode, stat);
+			stat->mode = fi->orig_i_mode;
+		}
+	}
+
+	if (refreshed != NULL)
+		*refreshed = r;
+
+	return err;
+}
+
 /*
  * Calling into a user-controlled filesystem gives the filesystem
  * daemon ptrace-like capabilities over the requester process.  This
@@ -862,14 +887,9 @@ static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
 	 */
 	if ((fc->flags & FUSE_DEFAULT_PERMISSIONS) ||
 	    ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))) {
-		struct fuse_inode *fi = get_fuse_inode(inode);
-		if (fi->i_time < get_jiffies_64()) {
-			err = fuse_do_getattr(inode, NULL, NULL);
-			if (err)
-				return err;
-
-			refreshed = true;
-		}
+		err = fuse_update_attributes(inode, NULL, NULL, &refreshed);
+		if (err)
+			return err;
 	}
 
 	if (fc->flags & FUSE_DEFAULT_PERMISSIONS) {
@@ -1173,22 +1193,12 @@ static int fuse_getattr(struct vfsmount *mnt, struct dentry *entry,
 			struct kstat *stat)
 {
 	struct inode *inode = entry->d_inode;
-	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_conn *fc = get_fuse_conn(inode);
-	int err;
 
 	if (!fuse_allow_task(fc, current))
 		return -EACCES;
 
-	if (fi->i_time < get_jiffies_64())
-		err = fuse_do_getattr(inode, stat, NULL);
-	else {
-		err = 0;
-		generic_fillattr(inode, stat);
-		stat->mode = fi->orig_i_mode;
-	}
-
-	return err;
+	return fuse_update_attributes(inode, stat, NULL, NULL);
 }
 
 static int fuse_setxattr(struct dentry *entry, const char *name,