From a220ac0970ad84e357168bd3f759ec57ef795885 Mon Sep 17 00:00:00 2001 From: Jaroslav Rohel Date: Wed, 21 Aug 2024 09:45:52 +0200 Subject: [PATCH] [libdnf, actions plugin] Pipe and OnScopeExit in execute_command To ensure the release of resources after an exception. --- libdnf5-plugins/actions/actions.cpp | 123 ++++++++++++++++++++-------- 1 file changed, 89 insertions(+), 34 deletions(-) diff --git a/libdnf5-plugins/actions/actions.cpp b/libdnf5-plugins/actions/actions.cpp index 9388744fd..606c9f2f3 100644 --- a/libdnf5-plugins/actions/actions.cpp +++ b/libdnf5-plugins/actions/actions.cpp @@ -1748,49 +1748,102 @@ void Actions::process_json_command(const CommandToRun & command, struct json_obj } -void Actions::execute_command(CommandToRun & command) { +class Pipe { +public: + Pipe() { + if (pipe(fds) == -1) { + throw ActionsPluginError(M_("Cannot create pipe: {}"), std::string{std::strerror(errno)}); + } + } + + Pipe(const Pipe &) = delete; + Pipe & operator=(const Pipe &) = delete; + + Pipe(Pipe && other) noexcept { *this = std::move(other); } + + Pipe & operator=(Pipe && pipe) noexcept { + if (this != &pipe) { + fds[PipeEnd::READ] = pipe.fds[PipeEnd::READ]; + fds[PipeEnd::WRITE] = pipe.fds[PipeEnd::WRITE]; + pipe.fds[PipeEnd::READ] = -1; + pipe.fds[PipeEnd::WRITE] = -1; + } + return *this; + } + + int get_in() const noexcept { return fds[PipeEnd::READ]; } + int get_out() const noexcept { return fds[PipeEnd::WRITE]; } + + void close_in() noexcept { close(PipeEnd::READ); } + void close_out() noexcept { close(PipeEnd::WRITE); } + + ~Pipe() { + close_in(); + close_out(); + } + +private: enum PipeEnd { READ = 0, WRITE = 1 }; - auto & base = get_base(); - int pipe_out_from_child[2]; - int pipe_to_child[2]; - if (pipe(pipe_to_child) == -1) { - base.get_logger()->error("Actions plugin: Cannot create pipe: {}", std::strerror(errno)); - return; + void close(int fd_idx) noexcept { + if (fds[fd_idx] != -1) { + ::close(fds[fd_idx]); + fds[fd_idx] = -1; + } } - if (pipe(pipe_out_from_child) == -1) { - auto errnum = errno; - close(pipe_to_child[PipeEnd::WRITE]); - close(pipe_to_child[PipeEnd::READ]); - base.get_logger()->error("Actions plugin: Cannot create pipe: {}", std::strerror(errnum)); - return; + + int fds[2]; +}; + + +/// The class template OnScopeExit is a general-purpose scope guard +/// intended to call its exit function when a scope is exited. +template + requires requires(TExitFunction f) { + { f() } noexcept; } +class OnScopeExit { +public: + OnScopeExit(TExitFunction && function) noexcept : exit_function{std::move(function)} {} + + ~OnScopeExit() noexcept { exit_function(); } + + OnScopeExit(const OnScopeExit &) = delete; + OnScopeExit(OnScopeExit &&) = delete; + OnScopeExit & operator=(const OnScopeExit &) = delete; + OnScopeExit & operator=(OnScopeExit &&) = delete; + +private: + TExitFunction exit_function; +}; + + +void Actions::execute_command(CommandToRun & command) { + auto & base = get_base(); + + Pipe pipe_out_from_child; + Pipe pipe_to_child; auto child_pid = fork(); if (child_pid == -1) { - auto errnum = errno; - close(pipe_to_child[PipeEnd::WRITE]); - close(pipe_to_child[PipeEnd::READ]); - close(pipe_out_from_child[PipeEnd::WRITE]); - close(pipe_out_from_child[PipeEnd::READ]); - base.get_logger()->error("Actions plugin: Cannot fork: {}", std::strerror(errnum)); + base.get_logger()->error("Actions plugin: Cannot fork: {}", std::strerror(errno)); } else if (child_pid == 0) { - close(pipe_to_child[PipeEnd::WRITE]); // close writing end of the pipe on the child side - close(pipe_out_from_child[PipeEnd::READ]); // close reading end of the pipe on the child side + pipe_to_child.close_out(); // close writing end of the pipe on the child side + pipe_out_from_child.close_in(); // close reading end of the pipe on the child side // bind stdin of the child process to the reading end of the pipe - if (dup2(pipe_to_child[PipeEnd::READ], fileno(stdin)) == -1) { + if (dup2(pipe_to_child.get_in(), fileno(stdin)) == -1) { base.get_logger()->error("Actions plugin: Cannot bind command stdin: {}", std::strerror(errno)); _exit(255); } - close(pipe_to_child[PipeEnd::READ]); + pipe_to_child.close_in(); // bind stdout of the child process to the writing end of the pipe - if (dup2(pipe_out_from_child[PipeEnd::WRITE], fileno(stdout)) == -1) { + if (dup2(pipe_out_from_child.get_out(), fileno(stdout)) == -1) { base.get_logger()->error("Actions plugin: Cannot bind command stdout: {}", std::strerror(errno)); _exit(255); } - close(pipe_out_from_child[PipeEnd::WRITE]); + pipe_out_from_child.close_out(); std::vector args; args.reserve(command.args.size() + 1); @@ -1810,22 +1863,24 @@ void Actions::execute_command(CommandToRun & command) { "Actions plugin: Cannot execute \"{}{}\": {}", command.command, args_string, std::strerror(errnum)); _exit(255); } else { - close(pipe_to_child[PipeEnd::READ]); - close(pipe_out_from_child[PipeEnd::WRITE]); + OnScopeExit finish([&pipe_to_child, &pipe_out_from_child, child_pid]() noexcept { + pipe_to_child.close_out(); + pipe_out_from_child.close_in(); + waitpid(child_pid, nullptr, 0); + }); + + pipe_to_child.close_in(); + pipe_out_from_child.close_out(); switch (command.action.mode) { case Action::Mode::PLAIN: - close(pipe_to_child[PipeEnd::WRITE]); // close immediately, don't send anything to child in PLAIN mode - process_plain_communication(command, pipe_out_from_child[PipeEnd::READ]); + pipe_to_child.close_out(); // close immediately, don't send anything to child in PLAIN mode + process_plain_communication(command, pipe_out_from_child.get_in()); break; case Action::Mode::JSON: - process_json_communication(command, pipe_out_from_child[PipeEnd::READ], pipe_to_child[PipeEnd::WRITE]); - close(pipe_to_child[PipeEnd::WRITE]); + process_json_communication(command, pipe_out_from_child.get_in(), pipe_to_child.get_out()); break; } - - close(pipe_out_from_child[PipeEnd::READ]); - waitpid(child_pid, nullptr, 0); } }