8fe8417ffb
In embedded development environments, due to the lack of address isolation between processes, fd may be passed between processes and lead to misuse, We have designed an fd cross-process automatic detection tool, fdcheck_protect returns the fd containing the pid information, indicating that the ownership of the current fd belongs to the pid and is not allowed to be used by other processes. fdcheck_restore will obtain the true fd and check if the ownership of the fd is legal For ease of understanding, let's give an example where the following information is represented in 32-bit binary format fd 00000000 00000000 00000000 10001010 pid 00000000 00000000 00000011 01010101 ret 00000000 00000011 01010101 10001010 Signed-off-by: hujun5 <hujun5@xiaomi.com>
128 lines
4.0 KiB
C
128 lines
4.0 KiB
C
/****************************************************************************
|
|
* libs/libc/misc/lib_fdcheck.c
|
|
*
|
|
* Licensed to the Apache Software Foundation (ASF) under one or more
|
|
* contributor license agreements. See the NOTICE file distributed with
|
|
* this work for additional information regarding copyright ownership. The
|
|
* ASF licenses this file to you under the Apache License, Version 2.0 (the
|
|
* "License"); you may not use this file except in compliance with the
|
|
* License. You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
* License for the specific language governing permissions and limitations
|
|
* under the License.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <nuttx/fdcheck.h>
|
|
#include <nuttx/lib/math32.h>
|
|
|
|
#include <debug.h>
|
|
#include <stdio.h>
|
|
|
|
#ifdef CONFIG_FDCHECK
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
#define FD_SHIFT 0
|
|
#define FD_BITS LOG2_CEIL(OPEN_MAX)
|
|
#define FD_MASK ((1 << FD_BITS) - 1)
|
|
|
|
#define PID_SHIFT (FD_BITS + FD_SHIFT)
|
|
#define PID_BITS (8 * sizeof(int) - 1 - PID_SHIFT)
|
|
#define PID_MASK ((1 << PID_BITS) - 1)
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: fdcheck_restore
|
|
*
|
|
* Description: Obtain original fd information
|
|
*
|
|
* Val carries the pid and fd information.
|
|
* The original fd information is stored in low bit of val.
|
|
* The pid information is stored in the high bit of val.
|
|
* For ease of understanding, let's give an example where
|
|
* the following information is represented in 32-bit binary format
|
|
*
|
|
* val 00000000 00000000 01010101 10001010
|
|
* fd 00000000 00000000 00000000 10001010
|
|
* pid 00000000 00000000 00000000 01010101
|
|
*
|
|
* In this function, we also check if the pid information is correct.
|
|
* If there is an error, it will panic.
|
|
*
|
|
* Input Parameters:
|
|
* val - this val carrying pid and original fd information
|
|
*
|
|
* Returned Value: none
|
|
*
|
|
****************************************************************************/
|
|
|
|
int fdcheck_restore(int val)
|
|
{
|
|
int pid_expect;
|
|
int pid_now;
|
|
|
|
if (val <= 2)
|
|
{
|
|
return val;
|
|
}
|
|
|
|
pid_expect = (val >> PID_SHIFT);
|
|
pid_now = (getpid() & PID_MASK);
|
|
if (pid_expect != pid_now)
|
|
{
|
|
ferr("pid_expect %d pid_now %d\n", pid_expect, pid_now);
|
|
PANIC();
|
|
}
|
|
|
|
return val & FD_MASK;
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: fdcheck_protect
|
|
*
|
|
* Description: Obtain the combined value of fd and pid
|
|
*
|
|
* the return value carries the pid and fd information.
|
|
* The original fd information is stored in low bit of val.
|
|
* The pid information is stored in high bit of val.
|
|
* For ease of understanding, let's give an example where
|
|
* the following information is represented in 32-bit binary format
|
|
*
|
|
* fd 00000000 00000000 00000000 10001010
|
|
* pid 00000000 00000000 00000000 01010101
|
|
* val 00000000 00000000 01010101 10001010
|
|
*
|
|
* Input Parameters:
|
|
* fd - original fd
|
|
*
|
|
* Returned Value: the combined value of fd and pid
|
|
*
|
|
****************************************************************************/
|
|
|
|
int fdcheck_protect(int fd)
|
|
{
|
|
if (fd <= 2)
|
|
{
|
|
return fd;
|
|
}
|
|
|
|
return (fd & FD_MASK) | ((getpid() & PID_MASK) << PID_SHIFT);
|
|
}
|
|
|
|
#endif
|