[PATCH 6.0 044/124] vfs: fix copy_file_range() averts filesystem freeze protection

Greg Kroah-Hartman
2022-12-05T19:24:38Z

From: Amir Goldstein <amir73il@gmail.com>

[ Upstream commit 10bc8e4af65946b727728d7479c028742321b60a ]

Commit 868f9f2f8e00 ("vfs: fix copy_file_range() regression in cross-fs
copies") removed fallback to generic_copy_file_range() for cross-fs
cases inside vfs_copy_file_range().

To preserve behavior of nfsd and ksmbd server-side-copy, the fallback to
generic_copy_file_range() was added in nfsd and ksmbd code, but that
call is missing sb_start_write(), fsnotify hooks and more.

Ideally, nfsd and ksmbd would pass a flag to vfs_copy_file_range() that
will take care of the fallback, but that code would be subtle and we got
vfs_copy_file_range() logic wrong too many times already.

Instead, add a flag to explicitly request vfs_copy_file_range() to
perform only generic_copy_file_range() and let nfsd and ksmbd use this
flag only in the fallback path.

This choise keeps the logic changes to minimum in the non-nfsd/ksmbd code
paths to reduce the risk of further regressions.

Fixes: 868f9f2f8e00 ("vfs: fix copy_file_range() regression in cross-fs copies")
Tested-by: Namjae Jeon <linkinjeon@kernel.org>
Tested-by: Luis Henriques <lhenriques@suse.de>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ksmbd/vfs.c | 6 +++---
fs/nfsd/vfs.c | 4 ++--
fs/read_write.c | 19 +++++++++++++++----
include/linux/fs.h | 8 ++++++++
4 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/fs/ksmbd/vfs.c b/fs/ksmbd/vfs.c
index 78d01033604c..c5c801e38b63 100644
--- a/fs/ksmbd/vfs.c
+++ b/fs/ksmbd/vfs.c
@@ -1784,9 +1784,9 @@ int ksmbd_vfs_copy_file_ranges(struct ksmbd_work *work,
ret = vfs_copy_file_range(src_fp->filp, src_off,
dst_fp->filp, dst_off, len, 0);
if (ret == -EOPNOTSUPP || ret == -EXDEV)
- ret = generic_copy_file_range(src_fp->filp, src_off,
- dst_fp->filp, dst_off,
- len, 0);
+ ret = vfs_copy_file_range(src_fp->filp, src_off,
+ dst_fp->filp, dst_off, len,
+ COPY_FILE_SPLICE);
if (ret < 0)
return ret;

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index f3cd614e1f1e..dc24d67d0ca4 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -572,8 +572,8 @@ ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst,
ret = vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0);

if (ret == -EOPNOTSUPP || ret == -EXDEV)
- ret = generic_copy_file_range(src, src_pos, dst, dst_pos,
- count, 0);
+ ret = vfs_copy_file_range(src, src_pos, dst, dst_pos, count,
+ COPY_FILE_SPLICE);
return ret;
}

diff --git a/fs/read_write.c b/fs/read_write.c
index 328ce8cf9a85..24b9668d6377 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1388,6 +1388,8 @@ 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)
{
+ lockdep_assert(sb_write_started(file_inode(file_out)->i_sb));
+
return do_splice_direct(file_in, &pos_in, file_out, &pos_out,
len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
}
@@ -1424,7 +1426,9 @@ static int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
* and several different sets of file_operations, but they all end up
* using the same ->copy_file_range() function pointer.
*/
- if (file_out->f_op->copy_file_range) {
+ if (flags & COPY_FILE_SPLICE) {
+ /* cross sb splice is allowed */
+ } else if (file_out->f_op->copy_file_range) {
if (file_in->f_op->copy_file_range !=
file_out->f_op->copy_file_range)
return -EXDEV;
@@ -1474,8 +1478,9 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
size_t len, unsigned int flags)
{
ssize_t ret;
+ bool splice = flags & COPY_FILE_SPLICE;

- if (flags != 0)
+ if (flags & ~COPY_FILE_SPLICE)
return -EINVAL;

ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len,
@@ -1501,14 +1506,14 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
* same sb using clone, but for filesystems where both clone and copy
* are supported (e.g. nfs,cifs), we only call the copy method.
*/
- if (file_out->f_op->copy_file_range) {
+ if (!splice && file_out->f_op->copy_file_range) {
ret = file_out->f_op->copy_file_range(file_in, pos_in,
file_out, pos_out,
len, flags);
goto done;
}

- if (file_in->f_op->remap_file_range &&
+ if (!splice && file_in->f_op->remap_file_range &&
file_inode(file_in)->i_sb == file_inode(file_out)->i_sb) {
ret = file_in->f_op->remap_file_range(file_in, pos_in,
file_out, pos_out,
@@ -1528,6 +1533,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
* consistent story about which filesystems support copy_file_range()
* and which filesystems do not, that will allow userspace tools to
* make consistent desicions w.r.t using copy_file_range().
+ *
+ * We also get here if caller (e.g. nfsd) requested COPY_FILE_SPLICE.
*/
ret = generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
flags);
@@ -1582,6 +1589,10 @@ SYSCALL_DEFINE6(copy_file_range, int, fd_in, loff_t __user *, off_in,
pos_out = f_out.file->f_pos;
}

+ ret = -EINVAL;
+ if (flags != 0)
+ goto out;
+
ret = vfs_copy_file_range(f_in.file, pos_in, f_out.file, pos_out, len,
flags);
if (ret > 0) {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7203f5582fd4..be074b6895b9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2087,6 +2087,14 @@ struct dir_context {
*/
#define REMAP_FILE_ADVISORY (REMAP_FILE_CAN_SHORTEN)

+/*
+ * These flags control the behavior of vfs_copy_file_range().
+ * They are not available to the user via syscall.
+ *
+ * COPY_FILE_SPLICE: call splice direct instead of fs clone/copy ops
+ */
+#define COPY_FILE_SPLICE (1 << 0)
+
struct iov_iter;
struct io_uring_cmd;

--
2.35.1