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 632561D0F7E; Wed, 2 Oct 2024 14:49:31 +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=1727880571; cv=none; b=L43aOSDSRvPlUTjvVRqxL5GPAfBw5ei9bhUPNGl2KgniCxp1II/d8YY+dx0nwT7y6gDlnp99XzmZPU1/i01ylpERPtLcLsIQ9ig4kgAR8SAjHOSHM8iv0BJrxxk/aeXv+GBDetbxXncQlhylUwbPU/kU5Ibnl2SGIB1rHOBPUdE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727880571; c=relaxed/simple; bh=7sBf3pYhGVxhCefK+LYGF/NNuJVNtbt6Mx57xkg9osQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iY95DpWcE3LHX/436CBC8WtnCRt7TdWSqPRk3f6bGeXFe8cEJ7XZjsBok6UKbzLnyrbIYR3y/xqNhGhbd9TH1jRZ42Tkjx7m49As9oC2oJi8/KTaTtLYne4qV0Bi3/XZ4clm/yKbe6Dnv3WdhTDtqjg7hbhsBPCijEhH1RZck7w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XD3hPhy1; 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="XD3hPhy1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DFB16C4CEC2; Wed, 2 Oct 2024 14:49:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1727880571; bh=7sBf3pYhGVxhCefK+LYGF/NNuJVNtbt6Mx57xkg9osQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XD3hPhy1WfE54piHRtll9Ys7ip3b0IdwHglf2oGPxEccR76kfMfrsNFfkdfUeOl7Q F2Ssuji5H7mjjb1zhN41qQuo3O8IPqEzmq0ytnDqlPZr7kIXXG1ltjZ3RU7iZlhcnp RzdAxJADHLqxhi9CNyuH4zikSPSiP1plVtxUegyQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+67ba3c42bcbb4665d3ad@syzkaller.appspotmail.com, Julian Sun , Jan Kara , Christian Brauner Subject: [PATCH 6.6 474/538] vfs: fix race between evice_inodes() and find_inode()&iput() Date: Wed, 2 Oct 2024 15:01:53 +0200 Message-ID: <20241002125811.154543043@linuxfoundation.org> X-Mailer: git-send-email 2.46.2 In-Reply-To: <20241002125751.964700919@linuxfoundation.org> References: <20241002125751.964700919@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org 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: Julian Sun commit 88b1afbf0f6b221f6c5bb66cc80cd3b38d696687 upstream. Hi, all Recently I noticed a bug[1] in btrfs, after digged it into and I believe it'a race in vfs. Let's assume there's a inode (ie ino 261) with i_count 1 is called by iput(), and there's a concurrent thread calling generic_shutdown_super(). cpu0: cpu1: iput() // i_count is 1 ->spin_lock(inode) ->dec i_count to 0 ->iput_final() generic_shutdown_super() ->__inode_add_lru() ->evict_inodes() // cause some reason[2] ->if (atomic_read(inode->i_count)) continue; // return before // inode 261 passed the above check // list_lru_add_obj() // and then schedule out ->spin_unlock() // note here: the inode 261 // was still at sb list and hash list, // and I_FREEING|I_WILL_FREE was not been set btrfs_iget() // after some function calls ->find_inode() // found the above inode 261 ->spin_lock(inode) // check I_FREEING|I_WILL_FREE // and passed ->__iget() ->spin_unlock(inode) // schedule back ->spin_lock(inode) // check (I_NEW|I_FREEING|I_WILL_FREE) flags, // passed and set I_FREEING iput() ->spin_unlock(inode) ->spin_lock(inode) ->evict() // dec i_count to 0 ->iput_final() ->spin_unlock() ->evict() Now, we have two threads simultaneously evicting the same inode, which may trigger the BUG(inode->i_state & I_CLEAR) statement both within clear_inode() and iput(). To fix the bug, recheck the inode->i_count after holding i_lock. Because in the most scenarios, the first check is valid, and the overhead of spin_lock() can be reduced. If there is any misunderstanding, please let me know, thanks. [1]: https://lore.kernel.org/linux-btrfs/000000000000eabe1d0619c48986@google.com/ [2]: The reason might be 1. SB_ACTIVE was removed or 2. mapping_shrinkable() return false when I reproduced the bug. Reported-by: syzbot+67ba3c42bcbb4665d3ad@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=67ba3c42bcbb4665d3ad CC: stable@vger.kernel.org Fixes: 63997e98a3be ("split invalidate_inodes()") Signed-off-by: Julian Sun Link: https://lore.kernel.org/r/20240823130730.658881-1-sunjunchao2870@gmail.com Reviewed-by: Jan Kara Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman --- fs/inode.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/fs/inode.c +++ b/fs/inode.c @@ -757,6 +757,10 @@ again: continue; spin_lock(&inode->i_lock); + if (atomic_read(&inode->i_count)) { + spin_unlock(&inode->i_lock); + continue; + } if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) { spin_unlock(&inode->i_lock); continue;