[PATCH v2] vfs: prevent copy_file_range to copy across devices

Luis Henriques
2021-02-15T15:44:55Z

Nicolas Boichat reported an issue when trying to use the copy_file_range
syscall on a tracefs file. It failed silently because the file content is
generated on-the-fly (reporting a size of zero) and copy_file_range needs
to know in advance how much data is present.

This commit restores the cross-fs restrictions that existed prior to
5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices") and
removes generic_copy_file_range() calls from ceph, cifs, fuse, and nfs.

Fixes: 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices")
Link: https://lore.kernel.org/linux-fsdevel/20210212044405.4120619-1-drinkcat@chromium.org/
Cc: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Luis Henriques <lhenriques@suse.de>
---
Changes since v1 (after Amir review)
- restored do_copy_file_range() helper
- return -EOPNOTSUPP if fs doesn't implement CFR
- updated commit description

fs/ceph/file.c | 21 +++-----------------
fs/cifs/cifsfs.c | 3 ---
fs/fuse/file.c | 21 +++-----------------
fs/nfs/nfs4file.c | 20 +++----------------
fs/read_write.c | 49 ++++++++++------------------------------------
include/linux/fs.h | 3 ---
6 files changed, 19 insertions(+), 98 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 209535d5b8d3..639bd7bfaea9 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -2261,9 +2261,9 @@ static ssize_t ceph_do_objects_copy(struct ceph_inode_info *src_ci, u64 *src_off
return bytes;
}

-static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
- struct file *dst_file, loff_t dst_off,
- size_t len, unsigned int flags)
+static ssize_t ceph_copy_file_range(struct file *src_file, loff_t src_off,
+ struct file *dst_file, loff_t dst_off,
+ size_t len, unsigned int flags)
{
struct inode *src_inode = file_inode(src_file);
struct inode *dst_inode = file_inode(dst_file);
@@ -2456,21 +2456,6 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
return ret;
}

-static ssize_t ceph_copy_file_range(struct file *src_file, loff_t src_off,
- struct file *dst_file, loff_t dst_off,
- size_t len, unsigned int flags)
-{
- ssize_t ret;
-
- ret = __ceph_copy_file_range(src_file, src_off, dst_file, dst_off,
- len, flags);
-
- if (ret == -EOPNOTSUPP || ret == -EXDEV)
- ret = generic_copy_file_range(src_file, src_off, dst_file,
- dst_off, len, flags);
- return ret;
-}
-
const struct file_operations ceph_file_fops = {
.open = ceph_open,
.release = ceph_release,
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index ab883e84e116..7aa3d20f21c0 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1229,9 +1229,6 @@ static ssize_t cifs_copy_file_range(struct file *src_file, loff_t off,
len, flags);
free_xid(xid);

- if (rc == -EOPNOTSUPP || rc == -EXDEV)
- rc = generic_copy_file_range(src_file, off, dst_file,
- destoff, len, flags);
return rc;
}

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 8cccecb55fb8..0dd703278e49 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -3330,9 +3330,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
return err;
}

-static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in,
- struct file *file_out, loff_t pos_out,
- size_t len, unsigned int flags)
+static ssize_t fuse_copy_file_range(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ size_t len, unsigned int flags)
{
struct fuse_file *ff_in = file_in->private_data;
struct fuse_file *ff_out = file_out->private_data;
@@ -3439,21 +3439,6 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in,
return err;
}

-static ssize_t fuse_copy_file_range(struct file *src_file, loff_t src_off,
- struct file *dst_file, loff_t dst_off,
- size_t len, unsigned int flags)
-{
- ssize_t ret;
-
- ret = __fuse_copy_file_range(src_file, src_off, dst_file, dst_off,
- len, flags);
-
- if (ret == -EOPNOTSUPP || ret == -EXDEV)
- ret = generic_copy_file_range(src_file, src_off, dst_file,
- dst_off, len, flags);
- return ret;
-}
-
static const struct file_operations fuse_file_operations = {
.llseek = fuse_file_llseek,
.read_iter = fuse_file_read_iter,
diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index 57b3821d975a..60998209e310 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -133,9 +133,9 @@ nfs4_file_flush(struct file *file, fl_owner_t id)
}

#ifdef CONFIG_NFS_V4_2
-static ssize_t __nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
- struct file *file_out, loff_t pos_out,
- size_t count, unsigned int flags)
+static ssize_t nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ size_t count, unsigned int flags)
{
struct nfs42_copy_notify_res *cn_resp = NULL;
struct nl4_server *nss = NULL;
@@ -189,20 +189,6 @@ static ssize_t __nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
return ret;
}

-static ssize_t nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
- struct file *file_out, loff_t pos_out,
- size_t count, unsigned int flags)
-{
- ssize_t ret;
-
- ret = __nfs4_copy_file_range(file_in, pos_in, file_out, pos_out, count,
- flags);
- if (ret == -EOPNOTSUPP || ret == -EXDEV)
- ret = generic_copy_file_range(file_in, pos_in, file_out,
- pos_out, count, flags);
- return ret;
-}
-
static loff_t nfs4_file_llseek(struct file *filep, loff_t offset, int whence)
{
loff_t ret;
diff --git a/fs/read_write.c b/fs/read_write.c
index 75f764b43418..b217cd62ae0d 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1358,40 +1358,12 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
}
#endif

-/**
- * generic_copy_file_range - copy data between two files
- * @file_in: file structure to read from
- * @pos_in: file offset to read from
- * @file_out: file structure to write data to
- * @pos_out: file offset to write data to
- * @len: amount of data to copy
- * @flags: copy flags
- *
- * This is a generic filesystem helper to copy data from one file to another.
- * It has no constraints on the source or destination file owners - the files
- * can belong to different superblocks and different filesystem types. Short
- * copies are allowed.
- *
- * This should be called from the @file_out filesystem, as per the
- * ->copy_file_range() method.
- *
- * Returns the number of bytes copied or a negative error indicating the
- * failure.
- */
-
-ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
- struct file *file_out, loff_t pos_out,
- size_t len, unsigned int flags)
-{
- return do_splice_direct(file_in, &pos_in, file_out, &pos_out,
- len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
-}
-EXPORT_SYMBOL(generic_copy_file_range);
-
static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
size_t len, unsigned int flags)
{
+ ssize_t ret = -EXDEV;
+
/*
* Although we now allow filesystems to handle cross sb copy, passing
* a file of the wrong filesystem type to filesystem driver can result
@@ -1400,14 +1372,14 @@ static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
* several different file_system_type structures, but they all end up
* using the same ->copy_file_range() function pointer.
*/
- if (file_out->f_op->copy_file_range &&
- file_out->f_op->copy_file_range == file_in->f_op->copy_file_range)
- return file_out->f_op->copy_file_range(file_in, pos_in,
- file_out, pos_out,
- len, flags);
+ if (!file_out->f_op->copy_file_range)
+ ret = -EOPNOTSUPP;
+ else if (file_out->f_op->copy_file_range == file_in->f_op->copy_file_range)
+ ret = file_out->f_op->copy_file_range(file_in, pos_in,
+ file_out, pos_out,
+ len, flags);

- return generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
- flags);
+ return ret;
}

/*
@@ -1514,8 +1486,7 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
}

ret = do_copy_file_range(file_in, pos_in, file_out, pos_out, len,
- flags);
- WARN_ON_ONCE(ret == -EOPNOTSUPP);
+ flags);
done:
if (ret > 0) {
fsnotify_access(file_in);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index fd47deea7c17..3aaf627be409 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1910,9 +1910,6 @@ extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
loff_t, size_t, unsigned int);
-extern ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
- struct file *file_out, loff_t pos_out,
- size_t len, unsigned int flags);
extern int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t *count,