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[147.75.80.249]) by mx.google.com with ESMTPS id p7-20020a170906614700b00a38100b17d4si836021ejl.932.2024.02.06.03.45.03 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Feb 2024 03:45:03 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-54791-ouuuleilei=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249; Authentication-Results: mx.google.com; arc=pass (i=1); spf=pass (google.com: domain of linux-kernel+bounces-54791-ouuuleilei=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) smtp.mailfrom="linux-kernel+bounces-54791-ouuuleilei=gmail.com@vger.kernel.org" Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by am.mirrors.kernel.org (Postfix) with ESMTPS id 67C451F24CD7 for ; Tue, 6 Feb 2024 11:45:02 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8F95D1350CA; Tue, 6 Feb 2024 11:33:33 +0000 (UTC) Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 07924130E44; Tue, 6 Feb 2024 11:33:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707219211; cv=none; b=JMIy7SN1/iVX4fyB066M/6W3NhrMbM/0F1bIKycKRJwbPzHGx7NZUvmgjR6fN83jR9EGxuSqu4Jm/qlM/CMPB1uxFNEEXc9Cu4e9uVe0HpqCndpctxuYpo3ujkGCvBQ0Rgcwu5VjPpUUER6XHKym0XU7WABjZstXpYYZqjtiBFg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707219211; c=relaxed/simple; bh=1TOxKL8RRnNxulvXK50DzgvXwAnmOluv224Nju/yrew=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=A5CURwFB8zw/bOT+k/+44NQKkOfsdQS8nye+LyPe2NywbsxNGt/DmLPC27+shGB24ioM1W6sYSxSEqdzKfIrgd7CXq52UruTLynqa8p8ktBf7MOPTksZ/8LVMq9i8rLnfNydEVGEn9i989S7ZrbyJRym4JuNMrytBum9ib7bgLw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8BD5C41674; Tue, 6 Feb 2024 11:33:30 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rXJiB-00000006aIr-0AN3; Tue, 06 Feb 2024 06:33:59 -0500 Message-ID: <20240206113358.897028018@rostedt.homelinux.com> User-Agent: quilt/0.67 Date: Tue, 06 Feb 2024 06:32:03 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Linus Torvalds , Greg Kroah-Hartman , Sasha Levin , Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Al Viro , Christian Brauner Subject: [v6.7][PATCH v2 05/23] eventfs: Do ctx->pos update for all iterations in eventfs_iterate() References: <20240206113158.822006147@rostedt.homelinux.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790149817772533645 X-GMAIL-MSGID: 1790149817772533645 From: "Steven Rostedt (Google)" The ctx->pos was only updated when it added an entry, but the "skip to current pos" check (c--) happened for every loop regardless of if the entry was added or not. This inconsistency caused readdir to be incorrect. It was due to: for (i = 0; i < ei->nr_entries; i++) { if (c > 0) { c--; continue; } mutex_lock(&eventfs_mutex); /* If ei->is_freed then just bail here, nothing more to do */ if (ei->is_freed) { mutex_unlock(&eventfs_mutex); goto out; } r = entry->callback(name, &mode, &cdata, &fops); mutex_unlock(&eventfs_mutex); [..] ctx->pos++; } But this can cause the iterator to return a file that was already read. That's because of the way the callback() works. Some events may not have all files, and the callback can return 0 to tell eventfs to skip the file for this directory. for instance, we have: # ls /sys/kernel/tracing/events/ftrace/function format hist hist_debug id inject and # ls /sys/kernel/tracing/events/sched/sched_switch/ enable filter format hist hist_debug id inject trigger Where the function directory is missing "enable", "filter" and "trigger". That's because the callback() for events has: static int event_callback(const char *name, umode_t *mode, void **data, const struct file_operations **fops) { struct trace_event_file *file = *data; struct trace_event_call *call = file->event_call; [..] /* * Only event directories that can be enabled should have * triggers or filters, with the exception of the "print" * event that can have a "trigger" file. */ if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)) { if (call->class->reg && strcmp(name, "enable") == 0) { *mode = TRACE_MODE_WRITE; *fops = &ftrace_enable_fops; return 1; } if (strcmp(name, "filter") == 0) { *mode = TRACE_MODE_WRITE; *fops = &ftrace_event_filter_fops; return 1; } } if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE) || strcmp(trace_event_name(call), "print") == 0) { if (strcmp(name, "trigger") == 0) { *mode = TRACE_MODE_WRITE; *fops = &event_trigger_fops; return 1; } } [..] return 0; } Where the function event has the TRACE_EVENT_FL_IGNORE_ENABLE set. This means that the entries array elements for "enable", "filter" and "trigger" when called on the function event will have the callback return 0 and not 1, to tell eventfs to skip these files for it. Because the "skip to current ctx->pos" check happened for all entries, but the ctx->pos++ only happened to entries that exist, it would confuse the reading of a directory. Which would cause: # ls /sys/kernel/tracing/events/ftrace/function/ format hist hist hist_debug hist_debug id inject inject The missing "enable", "filter" and "trigger" caused ls to show "hist", "hist_debug" and "inject" twice. Update the ctx->pos for every iteration to keep its update and the "skip" update consistent. This also means that on error, the ctx->pos needs to be decremented if it was incremented without adding something. Link: https://lore.kernel.org/all/20240104150500.38b15a62@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240104220048.172295263@goodmis.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Linus Torvalds Cc: Al Viro Cc: Christian Brauner Cc: Greg Kroah-Hartman Fixes: 493ec81a8fb8e ("eventfs: Stop using dcache_readdir() for getdents()") Signed-off-by: Steven Rostedt (Google) (cherry picked from commit 1e4624eb5a0ecaae0d2c4e3019bece119725bb98) --- fs/tracefs/event_inode.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 0aca6910efb3..c73fb1f7ddbc 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -760,6 +760,8 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) continue; } + ctx->pos++; + if (ei_child->is_freed) continue; @@ -767,13 +769,12 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) dentry = create_dir_dentry(ei, ei_child, ei_dentry); if (!dentry) - goto out; + goto out_dec; ino = dentry->d_inode->i_ino; dput(dentry); if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR)) - goto out; - ctx->pos++; + goto out_dec; } for (i = 0; i < ei->nr_entries; i++) { @@ -784,6 +785,8 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) continue; } + ctx->pos++; + entry = &ei->entries[i]; name = entry->name; @@ -791,7 +794,7 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) /* If ei->is_freed then just bail here, nothing more to do */ if (ei->is_freed) { mutex_unlock(&eventfs_mutex); - goto out; + goto out_dec; } r = entry->callback(name, &mode, &cdata, &fops); mutex_unlock(&eventfs_mutex); @@ -800,19 +803,23 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); if (!dentry) - goto out; + goto out_dec; ino = dentry->d_inode->i_ino; dput(dentry); if (!dir_emit(ctx, name, strlen(name), ino, DT_REG)) - goto out; - ctx->pos++; + goto out_dec; } ret = 1; out: srcu_read_unlock(&eventfs_srcu, idx); return ret; + + out_dec: + /* Incremented ctx->pos without adding something, reset it */ + ctx->pos--; + goto out; } /**