linux-kernel - Need to know the size of data send from Kernel to USer Ap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <500E5808.1070607@gmail.com>
Date:	Tue, 24 Jul 2012 01:08:40 -0700
From:	bforce1729 <bforce1729@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Need to know the size of data send from Kernel to USer Ap

Hi,

I am new to kernel programming so can anyone point me to the right 
forum/reply for the question below.

I would like to implement a character device and using a node of type 
character  read and write data. However I am not sure of the length of 
data from kernel which a user app will receive, so I would like to code 
safely. If the data exceeds the application gets killed.
Any idea or API to perform the task of knowing the data length when 
passing data to and fro from kernel to user level would be appreciated.

Kernel code:

                 copy_to_user(buff, kernel_msg, strlen(kernel_msg));

User App:
                 fd=open("./my_device",O_RDONLY);
ret=read(fd,buff,strlen(buf));                        //How can I know 
the size of buff, which would be sent/filled from kernel???

Regards
bforce
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/