Luis Henriques <lhenriques@xxxxxxx> writes:
> Amir Goldstein <amir73il@xxxxxxxxx> writes:
>
>> On Fri, Feb 12, 2021 at 2:40 PM Luis Henriques <lhenriques@xxxxxxx> wrote:
> ...
>>> Sure, I just wanted to point out that *maybe* there are other options than
>>> simply reverting that commit :-)
>>>
>>> Something like the patch below (completely untested!) should revert to the
>>> old behaviour in filesystems that don't implement the CFR syscall.
>>>
>>> Cheers,
>>> --
>>> Luis
>>>
>>> diff --git a/fs/read_write.c b/fs/read_write.c
>>> index 75f764b43418..bf5dccc43cc9 100644
>>> --- a/fs/read_write.c
>>> +++ b/fs/read_write.c
>>> @@ -1406,8 +1406,11 @@ static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
>>> file_out, pos_out,
>>> len, flags);
>>>
>>> - return generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
>>> - flags);
>>> + if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
>>> + return -EXDEV;
>>> + else
>>> + generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
>>> + flags);
>>> }
>>>
>>
>> Which kernel is this patch based on?
>
> It was v5.11-rc7.
>
>> At this point, I am with Dave and Darrick on not falling back to
>> generic_copy_file_range() at all.
>>
>> We do not have proof of any workload that benefits from it and the
>> above patch does not protect from a wierd use case of trying to copy a file
>> from sysfs to sysfs.
>>
>
> Ok, cool. I can post a new patch doing just that. I guess that function
> do_copy_file_range() can be dropped in that case.
>
>> I am indecisive about what should be done with generic_copy_file_range()
>> called as fallback from within filesystems.
>>
>> I think the wise choice is to not do the fallback in any case, but this is up
>> to the specific filesystem maintainers to decide.
>
> I see what you mean. You're suggesting to have userspace handle all the
> -EOPNOTSUPP and -EXDEV errors. Would you rather have a patch that also
> removes all the calls to generic_copy_file_range() function? And that
> function can also be deleted too, of course.
Here's a first stab at this patch. Hopefully I didn't forgot anything
here. Let me know if you prefer the more conservative approach, i.e. not
touching any of the filesystems and let them use generic_copy_file_range.
Once everyone agrees on the final solution, I can follow-up with the
manpages update.
Cheers,
--
Luis
>From e1b37e80b12601d56f792bd19377d3e5208188ef Mon Sep 17 00:00:00 2001
From: Luis Henriques <lhenriques@xxxxxxx>
Date: Fri, 12 Feb 2021 18:03:23 +0000
Subject: [PATCH] vfs: prevent copy_file_range to copy across devices
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 effectively reverts 5dae222a5ff0 ("vfs: allow copy_file_range to
copy across devices"). Now the copy is done only if the filesystems for source
and destination files are the same and they implement this syscall.
Fixes: 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices")
Cc: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
Signed-off-by: Luis Henriques <lhenriques@xxxxxxx>
---
fs/ceph/file.c | 21 +++------------
fs/cifs/cifsfs.c | 3 ---
fs/fuse/file.c | 21 +++------------
fs/nfs/nfs4file.c | 20 +++-----------
fs/read_write.c | 65 ++++++++--------------------------------------
include/linux/fs.h | 3 ---
6 files changed, 20 insertions(+), 113 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 e46da536ed33..8b869cc67443 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..87bf9efd7f71 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1358,58 +1358,6 @@ 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)
-{
- /*
- * Although we now allow filesystems to handle cross sb copy, passing
- * a file of the wrong filesystem type to filesystem driver can result
- * in an attempt to dereference the wrong type of ->private_data, so
- * avoid doing that until we really have a good reason. NFS defines
- * 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);
-
- return generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
- flags);
-}
-
/*
* Performs necessary checks before doing a file copy
*
@@ -1474,6 +1422,14 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
{
ssize_t ret;
+ /*
+ * Allow the copy only if the filesystems for file_in and file_out are
+ * the same, and copy_file_range is implemented.
+ */
+ if (!file_out->f_op->copy_file_range ||
+ (file_out->f_op->copy_file_range != file_in->f_op->copy_file_range))
+ return -EXDEV;
+
if (flags != 0)
return -EINVAL;
@@ -1513,8 +1469,9 @@ 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);
+ ret = file_out->f_op->copy_file_range(file_in, pos_in,
+ file_out, pos_out,
+ len, flags);
WARN_ON_ONCE(ret == -EOPNOTSUPP);
done:
if (ret > 0) {
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,
