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b8e30b54ec
This patch is a rework of the NuttX file descriptor implementation. The goal is two-fold: 1. Improve POSIX compliance. The old implementation tied file description to inode only, not the file struct. POSIX however dictates otherwise. 2. Fix a bug with descriptor duplication (dup2() and dup3()). There is an existing race condition with this POSIX API that currently results in a kernel side crash. The crash occurs when a partially open / closed file descriptor is duplicated. The reason for the crash is that even if the descriptor is closed, the file might still be in use by the kernel (due to e.g. ongoing write to file). The open file data is changed by file_dup3() and this causes a crash in the device / drivers themselves as they lose access to the inode and private data. The fix is done by separating struct file into file and file descriptor structs. The file struct can live on even if the descriptor is closed, fixing the crash. This also fixes the POSIX issue, as two descriptors can now point to the same file. Signed-off-by: Ville Juven <ville.juven@unikie.com> Signed-off-by: dongjiuzhu1 <dongjiuzhu1@xiaomi.com>
99 lines
2.8 KiB
C
99 lines
2.8 KiB
C
/****************************************************************************
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* fs/vfs/fs_dup.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <unistd.h>
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#include <sched.h>
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <nuttx/fs/fs.h>
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#include "inode/inode.h"
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#include "sched/sched.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: file_dup
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*
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* Description:
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* Equivalent to the standard dup() function except that it
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* accepts a struct file instance instead of a file descriptor.
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*
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* Returned Value:
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* The new file descriptor is returned on success; a negated errno value
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* is returned on any failure.
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*
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****************************************************************************/
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int file_dup(FAR struct file *filep, int minfd, int flags)
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{
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return fdlist_dupfile(nxsched_get_fdlist_from_tcb(this_task()),
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flags, minfd, filep);
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}
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/****************************************************************************
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* Name: dup
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*
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* Description:
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* Clone a file or socket descriptor to an arbitrary descriptor number
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*
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****************************************************************************/
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int dup(int fd)
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{
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FAR struct file *filep;
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int ret;
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/* Get the file structure corresponding to the file descriptor. */
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ret = file_get(fd, &filep);
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if (ret < 0)
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{
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goto err;
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}
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/* Let file_dup() do the real work */
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ret = file_dup(filep, 0, 0);
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file_put(filep);
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if (ret < 0)
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{
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goto err;
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}
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return ret;
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err:
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set_errno(-ret);
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return ERROR;
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}
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