From mboxrd@z Thu Jan 1 00:00:00 1970 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 E19D5151CD6; Tue, 20 Feb 2024 21:24:04 +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=1708464245; cv=none; b=O8HwmqlAHR2VX1xJmCeoFtyrMnyTOUn7TPU70v6LfiskfjmNPPBVif/V2ek7DbSz/J0qeSJg51MMEOVguR6MEtI4WVuPOKLDypG7k0dv+hTRh4j0fJPRi7cnkF5emzw0DI+bHkl1Rlty2v3u1eF8RSfDXaTnWOfZhqa2hRexMbw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708464245; c=relaxed/simple; bh=pS049EuBGhcYHed2eRLgOJQKXYy1T9yJGbE+Ib33BLQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iBb0y737eKocohXd9PtURvdj55jK+z06OSoaiuhTRXbkmnsYvIeqkr6GL7Bg/RAhhxokYJHVIZw9kyxqpf/KX5N+uJ4anI8xaqinBm0zYo3RsWTO4p8ePiJCKd+xDpQZR4pL+Vm23LLCgouHWk68v0Mt7gSTePjbAgY+sp2pY8Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=B1Gw2tL1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="B1Gw2tL1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CDE4C433F1; Tue, 20 Feb 2024 21:24:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708464244; bh=pS049EuBGhcYHed2eRLgOJQKXYy1T9yJGbE+Ib33BLQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B1Gw2tL1AnM2oYW1dKrHOpBRJ+JKPa5rCPKdi2gQPjRnk7lOHSDxxSizOBp+dm8QZ wmmBxFWPO3yT4Vf4q5WtelS8Zb8MslRWZuzwJLhx+l+MCygFIul8aYmpP7tHzzOeiV Uo3fjADytt11WVH9zbTNdBfYm0Zv++nkaKG6pmco= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Linus Torvalds , Al Viro , Christian Brauner , "Steven Rostedt (Google)" Subject: [PATCH 6.6 296/331] eventfs: Do ctx->pos update for all iterations in eventfs_iterate() Date: Tue, 20 Feb 2024 21:56:52 +0100 Message-ID: <20240220205647.356924835@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240220205637.572693592@linuxfoundation.org> References: <20240220205637.572693592@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Steven Rostedt (Google)" commit 1e4624eb5a0ecaae0d2c4e3019bece119725bb98 upstream. 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) Signed-off-by: Greg Kroah-Hartman --- fs/tracefs/event_inode.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -760,6 +760,8 @@ static int eventfs_iterate(struct file * continue; } + ctx->pos++; + if (ei_child->is_freed) continue; @@ -767,13 +769,12 @@ static int eventfs_iterate(struct file * 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 * continue; } + ctx->pos++; + entry = &ei->entries[i]; name = entry->name; @@ -791,7 +794,7 @@ static int eventfs_iterate(struct file * /* 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 * 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; } /**