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vfs: move the generic write and copy checks out of mm
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The generic write check helpers also don't have much to do with the page
cache, so move them to the vfs.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
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@djwong
djwong committed Oct 15, 2020
1 parent 1b2c54d commit 407e9c6
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Showing 3 changed files with 143 additions and 146 deletions.
143 changes: 143 additions & 0 deletions fs/read_write.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1701,6 +1701,59 @@ static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
flags);
}

/*
* Performs necessary checks before doing a file copy
*
* Can adjust amount of bytes to copy via @req_count argument.
* Returns appropriate error code that caller should return or
* zero in case the copy should be allowed.
*/
static int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
size_t *req_count, unsigned int flags)
{
struct inode *inode_in = file_inode(file_in);
struct inode *inode_out = file_inode(file_out);
uint64_t count = *req_count;
loff_t size_in;
int ret;

ret = generic_file_rw_checks(file_in, file_out);
if (ret)
return ret;

/* Don't touch certain kinds of inodes */
if (IS_IMMUTABLE(inode_out))
return -EPERM;

if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
return -ETXTBSY;

/* Ensure offsets don't wrap. */
if (pos_in + count < pos_in || pos_out + count < pos_out)
return -EOVERFLOW;

/* Shorten the copy to EOF */
size_in = i_size_read(inode_in);
if (pos_in >= size_in)
count = 0;
else
count = min(count, size_in - (uint64_t)pos_in);

ret = generic_write_check_limits(file_out, pos_out, &count);
if (ret)
return ret;

/* Don't allow overlapped copying within the same file. */
if (inode_in == inode_out &&
pos_out + count > pos_in &&
pos_out < pos_in + count)
return -EINVAL;

*req_count = count;
return 0;
}

/*
* copy_file_range() differs from regular file read and write in that it
* specifically allows return partial success. When it does so is up to
Expand Down Expand Up @@ -1832,3 +1885,93 @@ SYSCALL_DEFINE6(copy_file_range, int, fd_in, loff_t __user *, off_in,
out2:
return ret;
}

/*
* Don't operate on ranges the page cache doesn't support, and don't exceed the
* LFS limits. If pos is under the limit it becomes a short access. If it
* exceeds the limit we return -EFBIG.
*/
int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)
{
struct inode *inode = file->f_mapping->host;
loff_t max_size = inode->i_sb->s_maxbytes;
loff_t limit = rlimit(RLIMIT_FSIZE);

if (limit != RLIM_INFINITY) {
if (pos >= limit) {
send_sig(SIGXFSZ, current, 0);
return -EFBIG;
}
*count = min(*count, limit - pos);
}

if (!(file->f_flags & O_LARGEFILE))
max_size = MAX_NON_LFS;

if (unlikely(pos >= max_size))
return -EFBIG;

*count = min(*count, max_size - pos);

return 0;
}

/*
* Performs necessary checks before doing a write
*
* Can adjust writing position or amount of bytes to write.
* Returns appropriate error code that caller should return or
* zero in case that write should be allowed.
*/
ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
loff_t count;
int ret;

if (IS_SWAPFILE(inode))
return -ETXTBSY;

if (!iov_iter_count(from))
return 0;

/* FIXME: this is for backwards compatibility with 2.4 */
if (iocb->ki_flags & IOCB_APPEND)
iocb->ki_pos = i_size_read(inode);

if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
return -EINVAL;

count = iov_iter_count(from);
ret = generic_write_check_limits(file, iocb->ki_pos, &count);
if (ret)
return ret;

iov_iter_truncate(from, count);
return iov_iter_count(from);
}
EXPORT_SYMBOL(generic_write_checks);

/*
* Performs common checks before doing a file copy/clone
* from @file_in to @file_out.
*/
int generic_file_rw_checks(struct file *file_in, struct file *file_out)
{
struct inode *inode_in = file_inode(file_in);
struct inode *inode_out = file_inode(file_out);

/* Don't copy dirs, pipes, sockets... */
if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
return -EISDIR;
if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
return -EINVAL;

if (!(file_in->f_mode & FMODE_READ) ||
!(file_out->f_mode & FMODE_WRITE) ||
(file_out->f_flags & O_APPEND))
return -EBADF;

return 0;
}
3 changes: 0 additions & 3 deletions include/linux/fs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3012,9 +3012,6 @@ extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
extern int generic_write_check_limits(struct file *file, loff_t pos,
loff_t *count);
extern int generic_file_rw_checks(struct file *file_in, struct file *file_out);
extern int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
size_t *count, unsigned int flags);
extern ssize_t generic_file_buffered_read(struct kiocb *iocb,
struct iov_iter *to, ssize_t already_read);
extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
Expand Down
143 changes: 0 additions & 143 deletions mm/filemap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3093,149 +3093,6 @@ struct page *read_cache_page_gfp(struct address_space *mapping,
}
EXPORT_SYMBOL(read_cache_page_gfp);

/*
* Don't operate on ranges the page cache doesn't support, and don't exceed the
* LFS limits. If pos is under the limit it becomes a short access. If it
* exceeds the limit we return -EFBIG.
*/
int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)
{
struct inode *inode = file->f_mapping->host;
loff_t max_size = inode->i_sb->s_maxbytes;
loff_t limit = rlimit(RLIMIT_FSIZE);

if (limit != RLIM_INFINITY) {
if (pos >= limit) {
send_sig(SIGXFSZ, current, 0);
return -EFBIG;
}
*count = min(*count, limit - pos);
}

if (!(file->f_flags & O_LARGEFILE))
max_size = MAX_NON_LFS;

if (unlikely(pos >= max_size))
return -EFBIG;

*count = min(*count, max_size - pos);

return 0;
}

/*
* Performs necessary checks before doing a write
*
* Can adjust writing position or amount of bytes to write.
* Returns appropriate error code that caller should return or
* zero in case that write should be allowed.
*/
inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
loff_t count;
int ret;

if (IS_SWAPFILE(inode))
return -ETXTBSY;

if (!iov_iter_count(from))
return 0;

/* FIXME: this is for backwards compatibility with 2.4 */
if (iocb->ki_flags & IOCB_APPEND)
iocb->ki_pos = i_size_read(inode);

if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
return -EINVAL;

count = iov_iter_count(from);
ret = generic_write_check_limits(file, iocb->ki_pos, &count);
if (ret)
return ret;

iov_iter_truncate(from, count);
return iov_iter_count(from);
}
EXPORT_SYMBOL(generic_write_checks);

/*
* Performs common checks before doing a file copy/clone
* from @file_in to @file_out.
*/
int generic_file_rw_checks(struct file *file_in, struct file *file_out)
{
struct inode *inode_in = file_inode(file_in);
struct inode *inode_out = file_inode(file_out);

/* Don't copy dirs, pipes, sockets... */
if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
return -EISDIR;
if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
return -EINVAL;

if (!(file_in->f_mode & FMODE_READ) ||
!(file_out->f_mode & FMODE_WRITE) ||
(file_out->f_flags & O_APPEND))
return -EBADF;

return 0;
}

/*
* Performs necessary checks before doing a file copy
*
* Can adjust amount of bytes to copy via @req_count argument.
* Returns appropriate error code that caller should return or
* zero in case the copy should be allowed.
*/
int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
size_t *req_count, unsigned int flags)
{
struct inode *inode_in = file_inode(file_in);
struct inode *inode_out = file_inode(file_out);
uint64_t count = *req_count;
loff_t size_in;
int ret;

ret = generic_file_rw_checks(file_in, file_out);
if (ret)
return ret;

/* Don't touch certain kinds of inodes */
if (IS_IMMUTABLE(inode_out))
return -EPERM;

if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
return -ETXTBSY;

/* Ensure offsets don't wrap. */
if (pos_in + count < pos_in || pos_out + count < pos_out)
return -EOVERFLOW;

/* Shorten the copy to EOF */
size_in = i_size_read(inode_in);
if (pos_in >= size_in)
count = 0;
else
count = min(count, size_in - (uint64_t)pos_in);

ret = generic_write_check_limits(file_out, pos_out, &count);
if (ret)
return ret;

/* Don't allow overlapped copying within the same file. */
if (inode_in == inode_out &&
pos_out + count > pos_in &&
pos_out < pos_in + count)
return -EINVAL;

*req_count = count;
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)
Expand Down

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