[LU-8774] copy_from_user() should not use MAX_STRING_SIZE

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.9.0
• Affects Version/s: Lustre 2.9.0
• Severity: 3
• Assignee: Jian Yu
• Reporter: Jian Yu

Description

The following codes are incorrect:

$ git grep "MAX_STRING_SIZE" | grep copy_from_user
lustre/ldlm/ldlm_resource.c:	if (copy_from_user(dummy, buffer, MAX_STRING_SIZE))
lustre/obdclass/lprocfs_status.c:	if (copy_from_user(dummy, buffer, MAX_STRING_SIZE))

We should only copy enough bytes to cover count passed in.