splice: don't pass the address of ->f_pos to methods

Signed-off-by: Al Viro <[email protected]>

fs/internal.h

@@ -131,6 +131,12 @@ extern struct dentry *__d_alloc(struct super_block *, const struct qstr *);
  */
 extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
 
+/*
+ * splice.c
+ */
+extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
+		loff_t *opos, size_t len, unsigned int flags);
+
 /*
  * pipe.c
  */

fs/read_write.c

@@ -1064,6 +1064,7 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 	struct fd in, out;
 	struct inode *in_inode, *out_inode;
 	loff_t pos;
+	loff_t out_pos;
 	ssize_t retval;
 	int fl;
 
@@ -1077,12 +1078,14 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 	if (!(in.file->f_mode & FMODE_READ))
 		goto fput_in;
 	retval = -ESPIPE;
-	if (!ppos)
-		ppos = &in.file->f_pos;
-	else
+	if (!ppos) {
+		pos = in.file->f_pos;
+	} else {
+		pos = *ppos;
 		if (!(in.file->f_mode & FMODE_PREAD))
 			goto fput_in;
-	retval = rw_verify_area(READ, in.file, ppos, count);
+	}
+	retval = rw_verify_area(READ, in.file, &pos, count);
 	if (retval < 0)
 		goto fput_in;
 	count = retval;
@@ -1099,15 +1102,15 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 	retval = -EINVAL;
 	in_inode = file_inode(in.file);
 	out_inode = file_inode(out.file);
-	retval = rw_verify_area(WRITE, out.file, &out.file->f_pos, count);
+	out_pos = out.file->f_pos;
+	retval = rw_verify_area(WRITE, out.file, &out_pos, count);
 	if (retval < 0)
 		goto fput_out;
 	count = retval;
 
 	if (!max)
 		max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);
 
-	pos = *ppos;
 	if (unlikely(pos + count > max)) {
 		retval = -EOVERFLOW;
 		if (pos >= max)
@@ -1126,18 +1129,23 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 	if (in.file->f_flags & O_NONBLOCK)
 		fl = SPLICE_F_NONBLOCK;
 #endif
-	retval = do_splice_direct(in.file, ppos, out.file, count, fl);
+	retval = do_splice_direct(in.file, &pos, out.file, &out_pos, count, fl);
 
 	if (retval > 0) {
 		add_rchar(current, retval);
 		add_wchar(current, retval);
 		fsnotify_access(in.file);
 		fsnotify_modify(out.file);
+		out.file->f_pos = out_pos;
+		if (ppos)
+			*ppos = pos;
+		else
+			in.file->f_pos = pos;
 	}
 
 	inc_syscr(current);
 	inc_syscw(current);
-	if (*ppos > max)
+	if (pos > max)
 		retval = -EOVERFLOW;
 
 fput_out:

fs/splice.c

@@ -1274,7 +1274,7 @@ static int direct_splice_actor(struct pipe_inode_info *pipe,
 {
 	struct file *file = sd->u.file;
 
-	return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
+	return do_splice_from(pipe, file, sd->opos, sd->total_len,
 			      sd->flags);
 }
 
@@ -1294,14 +1294,15 @@ static int direct_splice_actor(struct pipe_inode_info *pipe,
  *
  */
 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
-		      size_t len, unsigned int flags)
+		      loff_t *opos, size_t len, unsigned int flags)
 {
 	struct splice_desc sd = {
 		.len		= len,
 		.total_len	= len,
 		.flags		= flags,
 		.pos		= *ppos,
 		.u.file		= out,
+		.opos		= opos,
 	};
 	long ret;
 
@@ -1325,7 +1326,7 @@ static long do_splice(struct file *in, loff_t __user *off_in,
 {
 	struct pipe_inode_info *ipipe;
 	struct pipe_inode_info *opipe;
-	loff_t offset, *off;
+	loff_t offset;
 	long ret;
 
 	ipipe = get_pipe_info(in);
@@ -1356,13 +1357,15 @@ static long do_splice(struct file *in, loff_t __user *off_in,
 				return -EINVAL;
 			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
 				return -EFAULT;
-			off = &offset;
-		} else
-			off = &out->f_pos;
+		} else {
+			offset = out->f_pos;
+		}
 
-		ret = do_splice_from(ipipe, out, off, len, flags);
+		ret = do_splice_from(ipipe, out, &offset, len, flags);
 
-		if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
+		if (!off_out)
+			out->f_pos = offset;
+		else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
 			ret = -EFAULT;
 
 		return ret;
@@ -1376,13 +1379,15 @@ static long do_splice(struct file *in, loff_t __user *off_in,
 				return -EINVAL;
 			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
 				return -EFAULT;
-			off = &offset;
-		} else
-			off = &in->f_pos;
+		} else {
+			offset = in->f_pos;
+		}
 
-		ret = do_splice_to(in, off, opipe, len, flags);
+		ret = do_splice_to(in, &offset, opipe, len, flags);
 
-		if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
+		if (!off_in)
+			in->f_pos = offset;
+		else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
 			ret = -EFAULT;
 
 		return ret;

include/linux/fs.h

@@ -2414,8 +2414,6 @@ extern ssize_t generic_file_splice_write(struct pipe_inode_info *,
 		struct file *, loff_t *, size_t, unsigned int);
 extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
 		struct file *out, loff_t *, size_t len, unsigned int flags);
-extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
-		size_t len, unsigned int flags);
 
 extern void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);

include/linux/splice.h

@@ -35,6 +35,7 @@ struct splice_desc {
 		void *data;		/* cookie */
 	} u;
 	loff_t pos;			/* file position */
+	loff_t *opos;			/* sendfile: output position */
 	size_t num_spliced;		/* number of bytes already spliced */
 	bool need_wakeup;		/* need to wake up writer */
 };