[PATCH 02/28] vfs: check file ranges before cloning files

Darrick J. Wong
2018-10-22T00:30:20Z

Move the file range checks from vfs_clone_file_prep into a separate
generic_remap_checks function so that all the checks are collected in a
central location. This forms the basis for adding more checks from
generic_write_checks that will make cloning's input checking more
consistent with write input checking.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
---
fs/ocfs2/refcounttree.c | 2 +
fs/read_write.c | 55 +++++++++----------------------------
fs/xfs/xfs_reflink.c | 2 +
include/linux/fs.h | 9 ++++--
mm/filemap.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 90 insertions(+), 47 deletions(-)

diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
index 7a5ee145c733..19e03936c5e1 100644
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -4850,7 +4850,7 @@ int ocfs2_reflink_remap_range(struct file *file_in,
(OCFS2_I(inode_out)->ip_flags & OCFS2_INODE_SYSTEM_FILE))
goto out_unlock;

- ret = vfs_clone_file_prep_inodes(inode_in, pos_in, inode_out, pos_out,
+ ret = vfs_clone_file_prep(file_in, pos_in, file_out, pos_out,
&len, is_dedupe);
if (ret <= 0)
goto out_unlock;
diff --git a/fs/read_write.c b/fs/read_write.c
index 260797b01851..d6e8e242a15f 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1717,13 +1717,12 @@ static int clone_verify_area(struct file *file, loff_t pos, u64 len, bool write)
* Returns: 0 for "nothing to clone", 1 for "something to clone", or
* the usual negative error code.
*/
-int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,
- struct inode *inode_out, loff_t pos_out,
- u64 *len, bool is_dedupe)
+int vfs_clone_file_prep(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ u64 *len, bool is_dedupe)
{
- loff_t bs = inode_out->i_sb->s_blocksize;
- loff_t blen;
- loff_t isize;
+ struct inode *inode_in = file_inode(file_in);
+ struct inode *inode_out = file_inode(file_out);
bool same_inode = (inode_in == inode_out);
int ret;

@@ -1740,10 +1739,10 @@ int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,
if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
return -EINVAL;

- isize = i_size_read(inode_in);
-
/* Zero length dedupe exits immediately; reflink goes to EOF. */
if (*len == 0) {
+ loff_t isize = i_size_read(inode_in);
+
if (is_dedupe || pos_in == isize)
return 0;
if (pos_in > isize)
@@ -1751,36 +1750,11 @@ int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,
*len = isize - pos_in;
}

- /* Ensure offsets don't wrap and the input is inside i_size */
- if (pos_in + *len < pos_in || pos_out + *len < pos_out ||
- pos_in + *len > isize)
- return -EINVAL;
-
- /* Don't allow dedupe past EOF in the dest file */
- if (is_dedupe) {
- loff_t disize;
-
- disize = i_size_read(inode_out);
- if (pos_out >= disize || pos_out + *len > disize)
- return -EINVAL;
- }
-
- /* If we're linking to EOF, continue to the block boundary. */
- if (pos_in + *len == isize)
- blen = ALIGN(isize, bs) - pos_in;
- else
- blen = *len;
-
- /* Only reflink if we're aligned to block boundaries */
- if (!IS_ALIGNED(pos_in, bs) || !IS_ALIGNED(pos_in + blen, bs) ||
- !IS_ALIGNED(pos_out, bs) || !IS_ALIGNED(pos_out + blen, bs))
- return -EINVAL;
-
- /* Don't allow overlapped reflink within the same file */
- if (same_inode) {
- if (pos_out + blen > pos_in && pos_out < pos_in + blen)
- return -EINVAL;
- }
+ /* Check that we don't violate system file offset limits. */
+ ret = generic_remap_checks(file_in, pos_in, file_out, pos_out, len,
+ is_dedupe);
+ if (ret)
+ return ret;

/* Wait for the completion of any pending IOs on both files */
inode_dio_wait(inode_in);
@@ -1813,7 +1787,7 @@ int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,

return 1;
}
-EXPORT_SYMBOL(vfs_clone_file_prep_inodes);
+EXPORT_SYMBOL(vfs_clone_file_prep);

int do_clone_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out, u64 len)
@@ -1851,9 +1825,6 @@ int do_clone_file_range(struct file *file_in, loff_t pos_in,
if (ret)
return ret;

- if (pos_in + len > i_size_read(inode_in))
- return -EINVAL;
-
ret = file_in->f_op->clone_file_range(file_in, pos_in,
file_out, pos_out, len);
if (!ret) {
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 42ea7bab9144..281d5f53f2ec 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1326,7 +1326,7 @@ xfs_reflink_remap_prep(
if (IS_DAX(inode_in) || IS_DAX(inode_out))
goto out_unlock;

- ret = vfs_clone_file_prep_inodes(inode_in, pos_in, inode_out, pos_out,
+ ret = vfs_clone_file_prep(file_in, pos_in, file_out, pos_out,
len, is_dedupe);
if (ret <= 0)
goto out_unlock;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 897eae8faee1..ba93a6e7dac4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1825,9 +1825,9 @@ extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
unsigned long, loff_t *, rwf_t);
extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
loff_t, size_t, unsigned int);
-extern int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,
- struct inode *inode_out, loff_t pos_out,
- u64 *len, bool is_dedupe);
+extern int vfs_clone_file_prep(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ u64 *count, bool is_dedupe);
extern int do_clone_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out, u64 len);
extern int vfs_clone_file_range(struct file *file_in, loff_t pos_in,
@@ -2967,6 +2967,9 @@ extern int sb_min_blocksize(struct super_block *, int);
extern int generic_file_mmap(struct file *, struct vm_area_struct *);
extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
+extern int generic_remap_checks(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ uint64_t *count, bool is_dedupe);
extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
extern ssize_t __generic_file_write_iter(struct kiocb *, struct iov_iter *);
extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);
diff --git a/mm/filemap.c b/mm/filemap.c
index 52517f28e6f4..47e6bfd45a91 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2974,6 +2974,75 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
}
EXPORT_SYMBOL(generic_write_checks);

+/*
+ * Performs necessary checks before doing a clone.
+ *
+ * Can adjust amount of bytes to clone.
+ * Returns appropriate error code that caller should return or
+ * zero in case the clone should be allowed.
+ */
+int generic_remap_checks(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ uint64_t *req_count, bool is_dedupe)
+{
+ struct inode *inode_in = file_in->f_mapping->host;
+ struct inode *inode_out = file_out->f_mapping->host;
+ uint64_t count = *req_count;
+ uint64_t bcount;
+ loff_t size_in, size_out;
+ loff_t bs = inode_out->i_sb->s_blocksize;
+
+ /* The start of both ranges must be aligned to an fs block. */
+ if (!IS_ALIGNED(pos_in, bs) || !IS_ALIGNED(pos_out, bs))
+ return -EINVAL;
+
+ /* Ensure offsets don't wrap. */
+ if (pos_in + count < pos_in || pos_out + count < pos_out)
+ return -EINVAL;
+
+ size_in = i_size_read(inode_in);
+ size_out = i_size_read(inode_out);
+
+ /* Dedupe requires both ranges to be within EOF. */
+ if (is_dedupe &&
+ (pos_in >= size_in || pos_in + count > size_in ||
+ pos_out >= size_out || pos_out + count > size_out))
+ return -EINVAL;
+
+ /* Ensure the infile range is within the infile. */
+ if (pos_in >= size_in)
+ return -EINVAL;
+ count = min(count, size_in - (uint64_t)pos_in);
+
+ /*
+ * If the user wanted us to link to the infile's EOF, round up to the
+ * next block boundary for this check.
+ *
+ * Otherwise, make sure the count is also block-aligned, having
+ * already confirmed the starting offsets' block alignment.
+ */
+ if (pos_in + count == size_in) {
+ bcount = ALIGN(size_in, bs) - pos_in;
+ } else {
+ if (!IS_ALIGNED(count, bs))
+ return -EINVAL;
+
+ bcount = count;
+ }
+
+ /* Don't allow overlapped cloning within the same file. */
+ if (inode_in == inode_out &&
+ pos_out + bcount > pos_in &&
+ pos_out < pos_in + bcount)
+ return -EINVAL;
+
+ /* For now we don't support changing the length. */
+ if (*req_count != count)
+ return -EINVAL;
+
+ return 0;
+}
+
int pagecache_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)