Commit 646955cd authored by Amir Goldstein's avatar Amir Goldstein Committed by Darrick J. Wong
Browse files

vfs: remove redundant checks from generic_remap_checks() 



The access limit checks on input file range in generic_remap_checks()
are redundant because the input file size is guaranteed to be within
limits and pos+len are already checked to be within input file size.

Beyond the fact that the check cannot fail, if it would have failed,
it could return -EFBIG for input file range error. There is no precedent
for that. -EFBIG is returned in syscalls that would change file length.

With that call removed, we can fold generic_access_check_limits() into
generic_write_check_limits().

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent a3171351

mm/filemap.c

+12 −21
Original line number Diff line number Diff line
@@ -2895,24 +2895,11 @@ EXPORT_SYMBOL(read_cache_page_gfp); 
 * LFS limits.  If pos is under the limit it becomes a short access.  If it

 * exceeds the limit we return -EFBIG.

 */

static int generic_access_check_limits(struct file *file, loff_t pos,

static 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;



	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;

}



static int generic_write_check_limits(struct file *file, loff_t pos,

				      loff_t *count)

{

	loff_t limit = rlimit(RLIMIT_FSIZE);



	if (limit != RLIM_INFINITY) {
@@ -2923,7 +2910,15 @@ static int generic_write_check_limits(struct file *file, loff_t pos, 
		*count = min(*count, limit - pos);

	}



	return generic_access_check_limits(file, pos, count);

	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;

}



/*
@@ -2963,7 +2958,7 @@ EXPORT_SYMBOL(generic_write_checks); 
/*

 * Performs necessary checks before doing a clone.

 *

 * Can adjust amount of bytes to clone.

 * Can adjust amount of bytes to clone via @req_count argument.

 * Returns appropriate error code that caller should return or

 * zero in case the clone should be allowed.

 */
@@ -3001,10 +2996,6 @@ int generic_remap_checks(struct file *file_in, loff_t pos_in, 
		return -EINVAL;

	count = min(count, size_in - (uint64_t)pos_in);



	ret = generic_access_check_limits(file_in, pos_in, &count);

	if (ret)

		return ret;



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

	if (ret)

		return ret;

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