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 A46AA4E7816; Tue, 13 Oct 2026 12:12:20 +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=1791893542; cv=none; b=FHlCqk1M7eLyZvp9/fyj7RRbMgxX1mAz9j8vBZy3GB/OHJFmJFyg83vxnnrFEIILuRWquinkibls8Qw6XcxWEsbDkLWMbWKnpIgS62eUpUy2JKBBYkrvyPri+Luz+s/EHgWFdDDWfwdIrR7kovwB+rKenV3sePb5UIGEEPJrx+U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791893542; c=relaxed/simple; bh=L/zXSm52vY3Ln4k1ze7xhBX/hM8jKZ3yZracaKKM004=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SrQmSu15FBzAB0cCe3bSkAAZlRXKN0h0pS0tXFKuH0PdapbCg/3g8PTIgabqdjqkBsmBNlHs4FmzTMLpgufoFB9v3WrOaSZ1i3ih5/xqdccZe7mgn3Qi5b8DF31v7iW42Qgpre1O/7yCVII33mZqrF/TyaLYIC5JawFitbPR5sY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zn0Dx5PK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zn0Dx5PK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0222B1F000FF; Tue, 13 Oct 2026 12:12:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791893540; bh=8x9WPjUQEQOciki+lLSI1Q8nMHlOf9w72T5+JMDohV4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zn0Dx5PKsDGKpkfFQJHoffIZezj0wsVzITnX/NUZRR99ZkYlrE7hilR4xUBme5VlH Fcy03Vy7EAJcdITw10HYBXLVbiJ28V7oMVPRnUvT33MFXBzixRKYFcnxvKAo6fzOlV cfsZoc4SsYMhWBcJLEP0R88VDyI7QZgyleUZapTU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Frank Sorenson , Steve French , Sasha Levin Subject: [PATCH 6.18 261/621] cifs: prevent readdir from changing file size due to stale directory metadata Date: Tue, 13 Oct 2026 13:34:16 +0200 Message-ID: <20261013112927.055299699@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112920.855194808@linuxfoundation.org> References: <20261013112920.855194808@linuxfoundation.org> User-Agent: quilt/0.69 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Frank Sorenson [ Upstream commit e8a8d54c2d508891c142a928fc7d298c4c8bd0dd ] Windows Server's directory enumeration metadata lags behind the actual file size after a write+close or rename. A concurrent readdir() in the window between close() returning to userspace and stat() being called overwrites the correct cached i_size with the stale server value, causing stat() to return the wrong size. Once _cifsFileInfo_put() removes the last writable handle from openFileList, is_size_safe_to_change() permits readdir to overwrite i_size. smb2_close_getattr() then stamps cifs_i->time = jiffies, making the corrupt cached value appear fresh to the next stat(). The existing check (see Fixes:) only blocked stale size updates while an active RW lease was held, not after the last writable handle closes. Add cifsInodeInfo->time_last_write, written via smp_store_release() at writable close and on setattr/truncate. is_size_safe_to_change() checks is_inode_writable() first (acquiring open_file_lock), then rejects a readdir size update if time_last_write falls within acregmax jiffies. The spinlock release in _cifsFileInfo_put() forms a store-release barrier that pairs with the spin_lock() (load-acquire) in is_inode_writable(), ensuring the subsequent smp_load_acquire() on time_last_write observes any update from a concurrent close(). When a size update is rejected and the server value differs from the cached one, cifs_i->time is cleared to force a fresh QUERY_INFO on the next stat(). readdir is also blocked from changing i_size while writable handles are open or an RW lease is held, even on direct-IO mounts. For deferred close (closetimeo > 0), time_last_write is refreshed at the actual server close in smb2_deferred_work_close() and in the cifs_close_deferred_file*() drain paths invoked by lease/oplock breaks and tcon teardown, anchoring the protection window to the real close time rather than the earlier userspace close. time_last_write == 0 skips the time_before() check to avoid false positives near boot on 32-bit systems where jiffies starts close to INITIAL_JIFFIES. Does not reproduce against Samba or with actimeo=0. Fixes: e4b61f3b1c67 ("cifs: prevent updating file size from server if we have a read/write lease") Signed-off-by: Frank Sorenson Signed-off-by: Steve French Stable-dep-of: c2f2e83e3bbc ("cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths") Signed-off-by: Sasha Levin --- fs/smb/client/cifsfs.c | 1 + fs/smb/client/cifsglob.h | 1 + fs/smb/client/file.c | 70 ++++++++++++++++++++++++++++++++++++---- fs/smb/client/inode.c | 7 +++- fs/smb/client/misc.c | 35 ++++++++++++++++---- 5 files changed, 101 insertions(+), 13 deletions(-) diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c index 30daa09ab1b6e..f63519a0b1d8e 100644 --- a/fs/smb/client/cifsfs.c +++ b/fs/smb/client/cifsfs.c @@ -474,6 +474,7 @@ cifs_alloc_inode(struct super_block *sb) return NULL; cifs_inode->cifsAttrs = ATTR_ARCHIVE; /* default */ cifs_inode->time = 0; + cifs_inode->time_last_write = 0; /* * Until the file is open and we have gotten oplock info back from the * server, can not assume caching of file data or metadata. diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h index 562967d44bf34..8d751026dd4a2 100644 --- a/fs/smb/client/cifsglob.h +++ b/fs/smb/client/cifsglob.h @@ -1579,6 +1579,7 @@ struct cifsInodeInfo { spinlock_t writers_lock; unsigned int writers; /* Number of writers on this inode */ unsigned long time; /* jiffies of last update of inode */ + unsigned long time_last_write; /* jiffies of last writable close or truncate */ u64 uniqueid; /* server inode number */ u64 createtime; /* creation time on server */ __u8 lease_key[SMB2_LEASE_KEY_SIZE]; /* lease key for this inode */ diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c index 1e557601804f3..07f98a8567d35 100644 --- a/fs/smb/client/file.c +++ b/fs/smb/client/file.c @@ -1414,11 +1414,21 @@ void smb2_deferred_work_close(struct work_struct *work) { struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo, deferred.work); + struct cifsInodeInfo *cinode = CIFS_I(d_inode(cfile->dentry)); - spin_lock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock); + spin_lock(&cinode->deferred_lock); cifs_del_deferred_close(cfile); cfile->deferred_close_scheduled = false; - spin_unlock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock); + spin_unlock(&cinode->deferred_lock); + /* + * Refresh time_last_write immediately before the actual server close + * so the protection window is anchored to the real close time, not + * the earlier userspace close time stored by cifs_close(). + */ + if (OPEN_FMODE(cfile->f_flags) & FMODE_WRITE) { + /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */ + smp_store_release(&cinode->time_last_write, jiffies); + } _cifsFileInfo_put(cfile, true, false); } @@ -1447,6 +1457,10 @@ int cifs_close(struct inode *inode, struct file *file) if (file->private_data != NULL) { cfile = file->private_data; file->private_data = NULL; + if (file->f_mode & FMODE_WRITE) { + /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */ + smp_store_release(&cinode->time_last_write, jiffies); + } dclose = kmalloc(sizeof(struct cifs_deferred_close), GFP_KERNEL); if ((cfile->status_file_deleted == false) && (smb2_can_defer_close(inode, dclose))) { @@ -3120,15 +3134,27 @@ static int is_inode_writable(struct cifsInodeInfo *cifs_inode) bool is_size_safe_to_change(struct cifsInodeInfo *cifsInode, __u64 end_of_file, bool from_readdir) { + struct cifs_sb_info *cifs_sb; + unsigned long tlw; + if (!cifsInode) return true; + cifs_sb = CIFS_SB(cifsInode->netfs.inode.i_sb); + if (is_inode_writable(cifsInode) || ((cifsInode->oplock & CIFS_CACHE_RW_FLG) != 0 && from_readdir)) { /* This inode is open for write at least once */ - struct cifs_sb_info *cifs_sb; - cifs_sb = CIFS_SB(cifsInode->netfs.inode.i_sb); + /* + * Readdir data is unreliable when we have writable handles or + * an exclusive lease -- never allow it to change i_size, even + * on direct-IO mounts where the server's directory metadata + * can still lag behind the actual file state. + */ + if (from_readdir) + return false; + if (cifs_sb_flags(cifs_sb) & CIFS_MOUNT_DIRECT_IO) { /* since no page cache to corrupt on directio we can change size safely */ @@ -3139,8 +3165,40 @@ bool is_size_safe_to_change(struct cifsInodeInfo *cifsInode, __u64 end_of_file, return true; return false; - } else - return true; + } + + /* + * No writable handles open. Check whether we are within the attribute + * cache validity window of a recent local modification. + * + * For the close() path: cifs_close() calls smp_store_release() on + * time_last_write before _cifsFileInfo_put() removes the handle under + * open_file_lock. That spin_unlock() is a store-release that pairs + * with the spin_lock() (load-acquire) in is_inode_writable() above, + * so if is_inode_writable() returned false the smp_load_acquire() + * below is guaranteed to observe any time_last_write update from a + * concurrent close(). + * + * For the setattr/truncate paths: those callers use smp_store_release() + * directly; the smp_load_acquire() below pairs with that store. There + * is no shared lock between setattr and readdir, so this relies on + * acquire-release semantics alone. The store propagation latency on + * weakly-ordered architectures (nanoseconds) is negligible relative to + * the acregmax window (seconds) and the readdir RPC round-trip + * (milliseconds), making this a sound design choice in practice. + * + * time_last_write == 0 means the inode has never been written locally; + * skip the window check to avoid false positives near boot time when + * jiffies is still close to INITIAL_JIFFIES on 32-bit systems. + */ + if (from_readdir) { + /* Pairs with smp_store_release() at close and truncate sites. */ + tlw = smp_load_acquire(&cifsInode->time_last_write); + if (tlw && time_before(jiffies, tlw + cifs_sb->ctx->acregmax)) + return false; + } + + return true; } void cifs_oplock_break(struct work_struct *work) diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c index aa3b275f33c9a..ebc3edf33d20e 100644 --- a/fs/smb/client/inode.c +++ b/fs/smb/client/inode.c @@ -236,6 +236,8 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr, if (is_size_safe_to_change(cifs_i, fattr->cf_eof, from_readdir)) { i_size_write(inode, fattr->cf_eof); inode->i_blocks = CIFS_INO_BLOCKS(fattr->cf_bytes); + } else if (from_readdir && i_size_read(inode) != fattr->cf_eof) { + cifs_i->time = 0; } if (S_ISLNK(fattr->cf_mode) && fattr->cf_symlink_target) { @@ -3123,8 +3125,11 @@ int cifs_file_set_size(const unsigned int xid, struct dentry *dentry, cifs_put_tlink(tlink); set_size_out: - if (rc == 0) + if (rc == 0) { + /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */ + smp_store_release(&cifsInode->time_last_write, jiffies); cifs_resize_file_locked(inode, size); + } return rc; } diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c index 9c32213e93796..0703e06aba1ed 100644 --- a/fs/smb/client/misc.c +++ b/fs/smb/client/misc.c @@ -791,7 +791,8 @@ cifs_close_deferred_file(struct cifsInodeInfo *cifs_inode) cifs_del_deferred_close(cfile); spin_unlock(&cifs_inode->deferred_lock); - tmp_list = kmalloc(sizeof(struct file_list), GFP_ATOMIC); + tmp_list = kmalloc_obj(struct file_list, + GFP_ATOMIC); if (tmp_list == NULL) break; tmp_list->cfile = cfile; @@ -802,7 +803,14 @@ cifs_close_deferred_file(struct cifsInodeInfo *cifs_inode) spin_unlock(&cifs_inode->open_file_lock); list_for_each_entry_safe(tmp_list, tmp_next_list, &file_head, list) { - _cifsFileInfo_put(tmp_list->cfile, false, false); + struct cifsFileInfo *cfile = tmp_list->cfile; + + if (OPEN_FMODE(cfile->f_flags) & FMODE_WRITE) { + /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */ + smp_store_release(&CIFS_I(d_inode(cfile->dentry))->time_last_write, + jiffies); + } + _cifsFileInfo_put(cfile, false, false); list_del(&tmp_list->list); kfree(tmp_list); } @@ -823,7 +831,8 @@ cifs_close_all_deferred_files(struct cifs_tcon *tcon) cifs_del_deferred_close(cfile); spin_unlock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock); - tmp_list = kmalloc(sizeof(struct file_list), GFP_ATOMIC); + tmp_list = kmalloc_obj(struct file_list, + GFP_ATOMIC); if (tmp_list == NULL) break; tmp_list->cfile = cfile; @@ -834,7 +843,14 @@ cifs_close_all_deferred_files(struct cifs_tcon *tcon) spin_unlock(&tcon->open_file_lock); list_for_each_entry_safe(tmp_list, tmp_next_list, &file_head, list) { - _cifsFileInfo_put(tmp_list->cfile, true, false); + struct cifsFileInfo *cfile = tmp_list->cfile; + + if (OPEN_FMODE(cfile->f_flags) & FMODE_WRITE) { + /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */ + smp_store_release(&CIFS_I(d_inode(cfile->dentry))->time_last_write, + jiffies); + } + _cifsFileInfo_put(cfile, true, false); list_del(&tmp_list->list); kfree(tmp_list); } @@ -893,7 +909,7 @@ void cifs_close_deferred_file_under_dentry(struct cifs_tcon *tcon, cifs_del_deferred_close(cfile); spin_unlock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock); - tmp_list = kmalloc(sizeof(struct file_list), GFP_ATOMIC); + tmp_list = kmalloc_obj(struct file_list, GFP_ATOMIC); if (tmp_list == NULL) break; tmp_list->cfile = cfile; @@ -903,7 +919,14 @@ void cifs_close_deferred_file_under_dentry(struct cifs_tcon *tcon, spin_unlock(&tcon->open_file_lock); list_for_each_entry_safe(tmp_list, tmp_next_list, &file_head, list) { - _cifsFileInfo_put(tmp_list->cfile, true, false); + struct cifsFileInfo *cfile = tmp_list->cfile; + + if (OPEN_FMODE(cfile->f_flags) & FMODE_WRITE) { + /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */ + smp_store_release(&CIFS_I(d_inode(cfile->dentry))->time_last_write, + jiffies); + } + _cifsFileInfo_put(cfile, true, false); list_del(&tmp_list->list); kfree(tmp_list); } -- 2.53.0