169 lines
5.9 KiB
C
169 lines
5.9 KiB
C
/*
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* Copyright (C) 2018 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#pragma once
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#include <stdbool.h>
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#include <stdint.h>
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#include <sys/cdefs.h>
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__BEGIN_DECLS
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/*
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* Error checking for close(2).
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*
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* Mishandling of file descriptor ownership is a common source of errors that
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* can be extremely difficult to diagnose. Mistakes like the following can
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* result in seemingly 'impossible' failures showing up on other threads that
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* happened to try to open a file descriptor between the buggy code's close and
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* fclose:
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*
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* int print(int fd) {
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* int rc;
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* char buf[128];
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* while ((rc = read(fd, buf, sizeof(buf))) > 0) {
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* printf("%.*s", rc);
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* }
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* close(fd);
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* }
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*
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* int bug() {
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* FILE* f = fopen("foo", "r");
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* print(fileno(f));
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* fclose(f);
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* }
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*
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* To make it easier to find this class of bugs, bionic provides a method to
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* require that file descriptors are closed by their owners. File descriptors
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* can be associated with tags with which they must be closed. This allows
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* objects that conceptually own an fd (FILE*, unique_fd, etc.) to use their
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* own address at the tag, to enforce that closure of the fd must come as a
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* result of their own destruction (fclose, ~unique_fd, etc.)
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*
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* By default, a file descriptor's tag is 0, and close(fd) is equivalent to
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* closing fd with the tag 0.
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*/
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/*
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* For improved diagnostics, the type of a file descriptors owner can be
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* encoded in the most significant byte of the owner tag. Values of 0 and 0xff
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* are ignored, which allows for raw pointers to be used as owner tags without
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* modification.
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*/
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enum android_fdsan_owner_type {
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/*
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* Generic Java or native owners.
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*
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* Generic Java objects always use 255 as their type, using identityHashCode
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* as the value of the tag, leaving bits 33-56 unset. Native pointers are sign
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* extended from 48-bits of virtual address space, and so can have the MSB
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* set to 255 as well. Use the value of bits 49-56 to distinguish between
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* these cases.
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*/
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ANDROID_FDSAN_OWNER_TYPE_GENERIC_00 = 0,
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ANDROID_FDSAN_OWNER_TYPE_GENERIC_FF = 255,
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/* FILE* */
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ANDROID_FDSAN_OWNER_TYPE_FILE = 1,
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/* DIR* */
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ANDROID_FDSAN_OWNER_TYPE_DIR = 2,
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/* android::base::unique_fd */
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ANDROID_FDSAN_OWNER_TYPE_UNIQUE_FD = 3,
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/* sqlite-owned file descriptors */
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ANDROID_FDSAN_OWNER_TYPE_SQLITE = 4,
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/* java.io.FileInputStream */
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ANDROID_FDSAN_OWNER_TYPE_FILEINPUTSTREAM = 251,
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/* java.io.FileOutputStream */
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ANDROID_FDSAN_OWNER_TYPE_FILEOUTPUTSTREAM = 252,
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/* java.io.RandomAccessFile */
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ANDROID_FDSAN_OWNER_TYPE_RANDOMACCESSFILE = 253,
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/* android.os.ParcelFileDescriptor */
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ANDROID_FDSAN_OWNER_TYPE_PARCELFILEDESCRIPTOR = 254,
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};
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/*
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* Create an owner tag with the specified type and least significant 56 bits of tag.
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*/
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uint64_t android_fdsan_create_owner_tag(enum android_fdsan_owner_type type, uint64_t tag) __INTRODUCED_IN_FUTURE __attribute__((__weak__));
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/*
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* Exchange a file descriptor's tag.
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*
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* Logs and aborts if the fd's tag does not match expected_tag.
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*/
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void android_fdsan_exchange_owner_tag(int fd, uint64_t expected_tag, uint64_t new_tag) __INTRODUCED_IN_FUTURE __attribute__((__weak__));
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/*
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* Close a file descriptor with a tag, and resets the tag to 0.
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*
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* Logs and aborts if the tag is incorrect.
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*/
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int android_fdsan_close_with_tag(int fd, uint64_t tag) __INTRODUCED_IN_FUTURE __attribute__((__weak__));
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enum android_fdsan_error_level {
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// No errors.
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ANDROID_FDSAN_ERROR_LEVEL_DISABLED,
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// Warn once(ish) on error, and then downgrade to ANDROID_FDSAN_ERROR_LEVEL_DISABLED.
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ANDROID_FDSAN_ERROR_LEVEL_WARN_ONCE,
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// Warn always on error.
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ANDROID_FDSAN_ERROR_LEVEL_WARN_ALWAYS,
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// Abort on error.
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ANDROID_FDSAN_ERROR_LEVEL_FATAL,
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};
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/*
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* Get the error level.
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*/
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enum android_fdsan_error_level android_fdsan_get_error_level() __INTRODUCED_IN_FUTURE __attribute__((__weak__));
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/*
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* Set the error level and return the previous state.
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*
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* Error checking is automatically disabled in the child of a fork, to maintain
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* compatibility with code that forks, blindly closes FDs, and then execs.
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*
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* In cases such as the zygote, where the child has no intention of calling
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* exec, call this function to reenable fdsan checks.
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*
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* This function is not thread-safe and does not synchronize with checks of the
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* value, and so should probably only be called in single-threaded contexts
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* (e.g. postfork).
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*/
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enum android_fdsan_error_level android_fdsan_set_error_level(enum android_fdsan_error_level new_level) __INTRODUCED_IN_FUTURE __attribute__((__weak__));
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__END_DECLS
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