From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792706616; b=LWgwlmZPrpIWsL183mJft+2wyBUNzxtUycbTl8S8xQCqdDMq1da12DYe50Sm4hIhj6kQ gRH1YHoqwYrYmPCiDHr5EZnmg7uDLbWjxQ8D1N8du79UyY+O8RNx/An2XSr0caidmbddo MnERZk0BHkEjmP+WNhclUVSvl7p3gGJsHwLoUdEn4e4w5i8XF75QdcXuotuYf5NADb9q5 cRZrHIEhS8xHTWOiqIEA6esbQU1jIFnkjZvcormkMd/yCEPQjG13ja6Wy1wArsB4Jps+d SSahYNqduYdX/mePMD2E6xpxUkRQ3DxpRpsusCPg3/u/s46sr4Jz9aGQgyrHLX8CWLw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792706616; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=qOqpsJc7AAWTBffBDxFBpmpv1CgMyzBVCT2a8Vh1xBw=; b=FYu70Px8G8duKyoydgNdZWCM+cbhLwR9Ql+hwDwK3psp9G+SW0qgpGorm0bIh7goPKjx a/u4gxnmZHG6ozJw+wMPGRdGj0uQYdOxurqebWZ7RItGMS/IIqW2lIJk8I/IO7hwIZyAY /gCT9R8iPS+tYwCGNj09P8N4rIH61Ykgj9jKsoouvvv7vXEnzVV1TbaGnesURZQ4jP/Mn oPAeckcXBxRG2YzJhgzciTsytJeuJz6Vgd7U76j/KyaCCch8xDaPnwu3ovEEpCaHL4Q5d KKxdBFwqUUXAboF+wwhRFoMovSXRsP+S32O8fWk/+6e03RAGu5VK1VXwBkhBseoQXHA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="SAJBK/hO"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7743606A31A for ; Thu, 22 Oct 2026 22:03:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=SAJBK/hO Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C1841F01825; Thu, 22 Oct 2026 22:03:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792706615; bh=qOqpsJc7AAWTBffBDxFBpmpv1CgMyzBVCT2a8Vh1xBw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=SAJBK/hO99fbCW2xhOKxDbd5+qQX1zmfsQisdtJKgksSShbuciIZKOndxP6HrH+mq FYO2sxiHTj+ONxwwvLt6dD20vw+uZAB8Kt9i++4LmPR0MY2+0Vj8JX6orjI4EBDigi 4MlmHikrJxJALQ/pNvoh54T/jMluxul1vrTNXVlqLjtJ16URxgkRiOC4RoUrk5QgVt 6AsyXT8p/wX5wu9DEexqVp/Kv2Nnz37gNd+EOViqPhcFDZUZmrHU58knbJiGXpkjpU Ev7HMqJpPUKyPw/sJcmrJDIzSH3Q1wgDiFU1PMah2DxhbYx+pKSlQrkfvuhfeRVb1v xlOc1y61SOeOQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Paulo Alcantara , Namjae Jeon , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , Bharath SM , Sasha Levin Subject: [PATCH 6.18.y] smb: client: fix data corruption with concurrent writes and O_TRUNC Date: Thu, 22 Oct 2026 18:03:33 -0400 Message-ID: <20261022220226.1992474-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026102256-failing-clinking-a4c8@gregkh> References: <2026102256-failing-clinking-a4c8@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Paulo Alcantara [ Upstream commit a8603b52b39f520ea8a34def74c23fba87396d3e ] cifs_do_truncate() flushes dirty pages with filemap_write_and_wait() and truncates the file on the server, but in the old code both operations ran without holding i_rwsem or invalidate_lock. A concurrent buffered write via netfs_perform_write() -- which only needs i_rwsem shared -- could dirty new pages after the flush but before the local truncation, and those pages would be silently discarded by cifs_setsize() -> truncate_pagecache(). Fix by acquiring inode_lock (exclusive i_rwsem) and filemap_invalidate_lock at the top of cifs_do_truncate(), so the entire flush-truncate-resize sequence is atomic with respect to: - buffered writes (blocked by exclusive i_rwsem, since netfs_start_io_write takes i_rwsem shared), - read page faults (blocked by exclusive invalidate_lock, since filemap_fault takes it shared), - writeback collection (blocked by netfs_wb_begin/netfs_wb_end around the server truncate and local resize, since netfs_writepages also acquires the wb lock). Fixes: 110fee6b9bb5 ("smb: client: fix missing timestamp updates with O_TRUNC") Signed-off-by: Paulo Alcantara Reviewed-by: Namjae Jeon Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org [ sashal: Replaced netfs_wb_begin()/netfs_wb_end() with direct wb_lock mutex operations. ] Signed-off-by: Sasha Levin --- fs/smb/client/file.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c index 53e457759d84c..e4281d0d12dd7 100644 --- a/fs/smb/client/file.c +++ b/fs/smb/client/file.c @@ -990,42 +990,50 @@ static int cifs_do_truncate(const unsigned int xid, struct dentry *dentry) struct cifs_tcon *tcon; int rc; - rc = filemap_write_and_wait(inode->i_mapping); - if (is_interrupt_error(rc)) + rc = inode_lock_killable(inode); + if (rc) return -ERESTARTSYS; + + filemap_invalidate_lock(inode->i_mapping); + + rc = filemap_write_and_wait(inode->i_mapping); + if (is_interrupt_error(rc)) { + rc = -ERESTARTSYS; + goto out; + } mapping_set_error(inode->i_mapping, rc); cfile = find_writable_file(cinode, FIND_WR_FSUID_ONLY); rc = cifs_file_flush(xid, inode, cfile); if (!rc) { if (cfile) { + struct netfs_inode *ictx = netfs_inode(inode); + tcon = tlink_tcon(cfile->tlink); server = tcon->ses->server; + mutex_lock(&ictx->wb_lock); rc = server->ops->set_file_size(xid, tcon, cfile, 0, false); if (!rc) { - inode_lock(inode); - filemap_invalidate_lock(inode->i_mapping); netfs_resize_file(&cinode->netfs, 0, true); cifs_setsize(inode, 0); - filemap_invalidate_unlock(inode->i_mapping); - inode_unlock(inode); cifs_invalidate_cache(inode, 0); } + mutex_unlock(&ictx->wb_lock); } else { /* * No cached handle; evict stale pages so they can't * be served after the file is later extended; let * the server's O_TRUNC open response set the i_size */ - inode_lock(inode); - filemap_invalidate_lock(inode->i_mapping); truncate_inode_pages(inode->i_mapping, 0); - filemap_invalidate_unlock(inode->i_mapping); - inode_unlock(inode); cifs_invalidate_cache(inode, 0); } } + +out: + filemap_invalidate_unlock(inode->i_mapping); + inode_unlock(inode); if (cfile) cifsFileInfo_put(cfile); return rc; -- 2.53.0