From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 BF53152BE59; Thu, 15 Oct 2026 13:34:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792071247; cv=none; b=fA/i/hhEiUIHFB0Mi3YBQql/3Izx9qGoHVDyusjzikpX0MpFWRo7iGu1VIHtxrmgaXk6EHp5kyec7qhLTXAxswwdBlJeD3fasHWV+ufO0nS2rXFQc7llGwc+qT34lRjfS3fijxhWbvEbLUY3J92/mCcDrC5ga68c1x9gKilmfSE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792071247; c=relaxed/simple; bh=NzjgoKSqPSjbYwgEQR0ht6nUFl9E/8V5nNxLCRxQd00=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=X7wMk3u5CqMkeQ1RYGwcLnz1taymsw0ypR9EnBihUGealrm2QhYaSUZTRs1WIULo1cFhvvua08ylO1vo14hCYKah3nsllHmo7+9Xea+p4cgU09qaYLDYXTc1+xb7QqN3f3sgdc+j5hGZXajeuv4bYagVT55n0R1TrFqnNmPb0O8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BdWcrNOS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BdWcrNOS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92EDC1F000C7; Thu, 15 Oct 2026 13:34:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792071245; bh=ohxQMm4+6T4AWLsYoE6Ve+xI6U19JmMjTGTIn0TAFO8=; h=Date:From:To:Cc:Subject:References; b=BdWcrNOSHi10EM+ZDfEpAF/liaYBkCSW8DM3oTBUM8Pvjt1Y5LBlZ/u9c227soT9w Bzd6RoeuNzNNu05W/ZvzlI6RWRmdMLVLAUI1SXW6AeMWsukiq/8DJgLtpPov8wjPoU PeThTfJ68I6qKPTbyvg6eeeUB2WSBlE2Uq3rboCZgxtof51owJqZwx0+iwRG6MQZrd v60CZPAMc0XB/fEMWiih1dWmO1CQqXsd6p4wpn8AUwGk0RZorhnn+Vp6c4TSoFEbOX gHyunyvJRMzUP2sAmU8r1OmXK88C4m/KG/SZc934yZ8E6XpSgi/zklCNE6fMz02QPc v5khSunVh54jQ== Received: from rostedt by gandalf with local (Exim 4.100.1) (envelope-from ) id 1xHLau-00000000Mgg-34HL; Thu, 15 Oct 2026 09:34:04 -0400 Message-ID: <20261015133404.546835597@kernel.org> User-Agent: quilt/0.69 Date: Thu, 15 Oct 2026 09:33:23 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , stable@vger.kernel.org, "Christian Brauner (Amutable)" Subject: [for-linus][PATCH 13/16] eventfs: Free the eventfs_inode after an rcu grace period too References: <20261015133310.731003448@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: Christian Brauner tracefs_d_revalidate() reads ->is_freed of the eventfs_inode that dentry->d_fsdata points to, and ->d_revalidate() is called in rcu pathwalk mode with nothing but rcu_read_lock() held. The dentry itself stays around for such a walker, but tracefs_d_release() drops its reference to the eventfs_inode when the dentry is killed, and release_ei() then frees it after a grace period of eventfs_srcu. An SRCU grace period doesn't wait for rcu_read_lock() sections, so the walker can read an eventfs_inode that is already gone. With a pathwalk held up in tracefs_d_revalidate() while the dentry goes away: BUG: KASAN: slab-use-after-free in tracefs_d_revalidate+0x76/0x90 Read of size 1 at addr ff1100010152d8d0 by task walker/97 Call Trace: tracefs_d_revalidate+0x76/0x90 lookup_fast+0x320/0x640 path_lookupat+0x160/0xb00 filename_lookup+0x1f1/0x5b0 vfs_statx+0xd7/0x3b0 vfs_fstatat+0x4d/0x90 __do_sys_newfstatat+0xa0/0x100 do_syscall_64+0x10e/0x5e0 entry_SYSCALL_64_after_hwframe+0x77/0x7f [...] Allocated by task 1: __kmalloc_cache_noprof+0x249/0x560 eventfs_create_dir+0x7a/0x590 event_create_dir+0x2fb/0xcf0 trace_add_event_call+0xbf/0x150 [...] Freed by task 11: kfree+0x1db/0x5b0 srcu_invoke_callbacks+0x3a3/0x620 process_one_work+0x937/0x1810 worker_thread+0x4f1/0xd60 Before commit 8e556432477e ("eventfs: Use SRCU for freeing eventfs_inodes") release_ei() used call_rcu(), which covered the walker, while eventfs_iterate() needs the SRCU grace period. Wait for both and chain call_rcu() from the SRCU callback. Cc: stable@vger.kernel.org Fixes: 8e556432477e ("eventfs: Use SRCU for freeing eventfs_inodes") Link: https://patch.msgid.link/20261009-work-fixes-rcu-v1-4-7446d2d335e6@kernel.org Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Steven Rostedt --- fs/tracefs/event_inode.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 6e3513b13cfa..090aca946717 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -91,6 +91,14 @@ static void free_ei_rcu(struct rcu_head *rcu) } } +/* read under eventfs_srcu and, by tracefs_d_revalidate(), in rcu pathwalk */ +static void free_ei_srcu(struct rcu_head *rcu) +{ + struct eventfs_inode *ei = container_of(rcu, struct eventfs_inode, rcu); + + call_rcu(&ei->rcu, free_ei_rcu); +} + /* * eventfs_inode reference count management. * @@ -112,7 +120,7 @@ static void release_ei(struct kref *ref) entry->release(entry->name, ei->data); } - call_srcu(&eventfs_srcu, &ei->rcu, free_ei_rcu); + call_srcu(&eventfs_srcu, &ei->rcu, free_ei_srcu); } static inline void put_ei(struct eventfs_inode *ei) -- 2.53.0