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 BF26B1D416E; Wed, 6 Nov 2024 12:12:22 +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=1730895142; cv=none; b=mH3R48fzmHR8pKR2Odc8v3UGRv1d9EU8gIOJ9ngW/CY1GTAE69f1fsUePX5gEoVyDALNvTScVA6sOA2hM6QWSDPVb4VFdr4fDsmPXaMMfn7IBpT21XzbnYIHQ/KhvPmrqK5iU1DDqvVOy0CkT+X3OcFWHKralXhNTyTnwLhdaS8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730895142; c=relaxed/simple; bh=f7tu5ws+MwtGir73hC0DdVP+ByFH+pbauwxOfhrd6KE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=azsSCIsJJ+gwjmr3saLYuUqy9JwtaXgFFvUNpEKL27j9EiNctHXlxX0u2CeWksKufgSOGECZOxMZTMZQ3DRWWMZdkkmDmsAIlfmIvEFgXWGghhiMzTRMhlWbIycFMQ9gH3JZjnIq4y+7Pecv/Mvd7/yq7irBtO9QuQulGRfkpKY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=wV09sw4A; 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="wV09sw4A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D907C4CECD; Wed, 6 Nov 2024 12:12:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1730895142; bh=f7tu5ws+MwtGir73hC0DdVP+ByFH+pbauwxOfhrd6KE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wV09sw4AwntbQZV3CcLspJrHKEr8FVv/OeQ/Vp3TMFprDXg7KjNAkhWJOohmnU9C4 NPfwXlQwzM1nucH8a6u+bNpsyXUAzNYZCAvp9eoxTg27n3IneF/dNDr3yFMRimVE4f Y+VtBwRqn199QwxIyzrnRazP2FSajwnCkF9wgk2Y= 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 4.19 118/350] vfs: fix race between evice_inodes() and find_inode()&iput() Date: Wed, 6 Nov 2024 13:00:46 +0100 Message-ID: <20241106120323.819094853@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241106120320.865793091@linuxfoundation.org> References: <20241106120320.865793091@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 4.19-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 @@ -616,6 +616,10 @@ 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;