From patchwork Sat Nov 2 05:08:02 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 13859972 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 87BAE156677; Sat, 2 Nov 2024 05:08:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=62.89.141.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730524123; cv=none; b=LYEHciHt/Swd2ScDBPJNf/P7njj1Kflwtie681ymoSL/scbusT453Wf6UCydd1vSnfX8q7ofFhgJvoj78/eGR15OjQV03WN4fOQAD9WE25maAcTYks4IWaDwDPBs9mHM7ckbX12daLtChpqC74j56GhLFcs83mm48ENFjgJrjw4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730524123; c=relaxed/simple; bh=IQsUsKxTYHR/UWSxnzKXVjsg4zRNBpAAmVoUHBiqT2s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jrgIuuoBayf0Pca48rH4lJbOKkDdInqQ7A2VJdpei5TG+PvMFgDj/ZeVy5Q2IlMAyRfAE75mil4ZuOzvxLzspPlN9cUJRhUKtjMrZBODDl+QAi8mc4zEDMQHpnU+jeNDpESGWDIf57gmC2eOicgHCyUdr1dWNh8kqh5Wme1KrgQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk; spf=none smtp.mailfrom=ftp.linux.org.uk; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b=bWJgUW5z; arc=none smtp.client-ip=62.89.141.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ftp.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="bWJgUW5z" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=/ON4xfM/I52yPPOjnFJDfTb7C6U4u5Iw3hGLWaLbWO8=; b=bWJgUW5zQ5ZP2IgHiJnXgfGOlx NrX92siEnSvGGWqQ55QdjRtH7qY0RiVgZp/CAyc86hZo05Aim0PoSuHmCb35Lp8hY4usCOvhVh1FZ sQ8VMoimGh8U8xCYd8+jZ/tF81LWuefB12Hew1zlugZTU0hPNpHFDohPIhaBEe8FS5hv3tPyVVc5L s/AHDxd0r7ikQf6WKp9b/0inya+Rb6prb9bd1wtG9LuMUuAeFM1M02d3sttmk7YDBobl5C1dJKHu1 f9CL6P4b5E24xxjKvzeQxJL0nS69gKoSVAe7KGbJ6qjo7QLVUZWLqkEZV5qAWhidw50a1LPMesFxl ATvlB9pw==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.98 #2 (Red Hat Linux)) id 1t76N9-0000000AHm8-2vHc; Sat, 02 Nov 2024 05:08:27 +0000 From: Al Viro To: linux-fsdevel@vger.kernel.org Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, cgroups@vger.kernel.org, kvm@vger.kernel.org, netdev@vger.kernel.org, torvalds@linux-foundation.org Subject: [PATCH v3 04/28] get rid of perf_fget_light(), convert kernel/events/core.c to CLASS(fd) Date: Sat, 2 Nov 2024 05:08:02 +0000 Message-ID: <20241102050827.2451599-4-viro@zeniv.linux.org.uk> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241102050827.2451599-1-viro@zeniv.linux.org.uk> References: <20241102050219.GA2450028@ZenIV> <20241102050827.2451599-1-viro@zeniv.linux.org.uk> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: Al Viro Lift fdget() and fdput() out of perf_fget_light(), turning it into is_perf_file(struct fd f). The life gets easier in both callers if we do fdget() unconditionally, including the case when we are given -1 instead of a descriptor - that avoids a reassignment in perf_event_open(2) and it avoids a nasty temptation in _perf_ioctl() where we must *not* lift output_event out of scope for output. Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- kernel/events/core.c | 49 +++++++++++++++----------------------------- 1 file changed, 16 insertions(+), 33 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index e3589c4287cb..85b209626dd7 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5998,18 +5998,9 @@ EXPORT_SYMBOL_GPL(perf_event_period); static const struct file_operations perf_fops; -static inline int perf_fget_light(int fd, struct fd *p) +static inline bool is_perf_file(struct fd f) { - struct fd f = fdget(fd); - if (!fd_file(f)) - return -EBADF; - - if (fd_file(f)->f_op != &perf_fops) { - fdput(f); - return -EBADF; - } - *p = f; - return 0; + return !fd_empty(f) && fd_file(f)->f_op == &perf_fops; } static int perf_event_set_output(struct perf_event *event, @@ -6057,20 +6048,14 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon case PERF_EVENT_IOC_SET_OUTPUT: { - int ret; + CLASS(fd, output)(arg); // arg == -1 => empty + struct perf_event *output_event = NULL; if (arg != -1) { - struct perf_event *output_event; - struct fd output; - ret = perf_fget_light(arg, &output); - if (ret) - return ret; + if (!is_perf_file(output)) + return -EBADF; output_event = fd_file(output)->private_data; - ret = perf_event_set_output(event, output_event); - fdput(output); - } else { - ret = perf_event_set_output(event, NULL); } - return ret; + return perf_event_set_output(event, output_event); } case PERF_EVENT_IOC_SET_FILTER: @@ -12664,7 +12649,6 @@ SYSCALL_DEFINE5(perf_event_open, struct perf_event_attr attr; struct perf_event_context *ctx; struct file *event_file = NULL; - struct fd group = EMPTY_FD; struct task_struct *task = NULL; struct pmu *pmu; int event_fd; @@ -12735,10 +12719,12 @@ SYSCALL_DEFINE5(perf_event_open, if (event_fd < 0) return event_fd; + CLASS(fd, group)(group_fd); // group_fd == -1 => empty if (group_fd != -1) { - err = perf_fget_light(group_fd, &group); - if (err) + if (!is_perf_file(group)) { + err = -EBADF; goto err_fd; + } group_leader = fd_file(group)->private_data; if (flags & PERF_FLAG_FD_OUTPUT) output_event = group_leader; @@ -12750,7 +12736,7 @@ SYSCALL_DEFINE5(perf_event_open, task = find_lively_task_by_vpid(pid); if (IS_ERR(task)) { err = PTR_ERR(task); - goto err_group_fd; + goto err_fd; } } @@ -13017,12 +13003,11 @@ SYSCALL_DEFINE5(perf_event_open, mutex_unlock(¤t->perf_event_mutex); /* - * Drop the reference on the group_event after placing the - * new event on the sibling_list. This ensures destruction - * of the group leader will find the pointer to itself in - * perf_group_detach(). + * File reference in group guarantees that group_leader has been + * kept alive until we place the new event on the sibling_list. + * This ensures destruction of the group leader will find + * the pointer to itself in perf_group_detach(). */ - fdput(group); fd_install(event_fd, event_file); return event_fd; @@ -13041,8 +13026,6 @@ SYSCALL_DEFINE5(perf_event_open, err_task: if (task) put_task_struct(task); -err_group_fd: - fdput(group); err_fd: put_unused_fd(event_fd); return err;