ima: Check for ERR_PTR from dentry_path() in validate_hash_algo()

In the Linux kernel, the following vulnerability has been resolved: ima: Check for ERR_PTR from dentry_path() in validate_hash_algo() dentry_path() returns ERR_PTR(-ENAMETOOLONG) when the path exceeds the buffer. validate_hash_algo() passes the result straight to integrity_audit_msg() without checking. ERR_PTR is not NULL, so integrity_audit_message() sees a valid pointer and calls strlen() on it, which faults: BUG: unable to handle page fault for address: ffffffffffffffdc RIP: 0010:strlen+0x30/0xa0 Call Trace: audit_log_untrustedstring+0x19/0x30 integrity_audit_message+0x366/0x4f0 ima_inode_setxattr+0x512/0x5f0 Check for IS_ERR() and use NULL instead, which makes the audit message skip the name= field instead of crashing.