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 207DF390C8A; Sat, 17 Oct 2026 16:24:21 +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=1792254263; cv=none; b=uIfqOAPDzsViqH+SqPjAAujW7RXiQtZxvMSXniX+yjZsgoRqdQoz2PRdE4lhnjOlLAt87v1G2Q1s8q1MY3zfRwP/B/12nNh/H8Kcb2QkVAmWEqHIfREfN3IqZ1PRcAW6c1lclQ271IaPc4/Hjo7WEsjWtwULHyeHtlqe19YB5js= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792254263; c=relaxed/simple; bh=Gmc9wwqiq1bUwHgKA3+KUh0g+3+ZnJzdJ8LADKuG9uc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ofof8pNfQJhvWpsUkaecUrjsTDvh4/VkR6I/2c+Ml7IOconOjWm7URfu/Knm+YR7kjEgAox6UJo8QPZZn2k6c2HsQcRKfhDH81vVI4f2tiF7JlzYrApgConnYDJIZ9fuqOgNC9Wgw7gaIRG1Bkt+WZPGXltY6UnTycczBjLRvc8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LwwDKu9x; 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="LwwDKu9x" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36EB61F000C4; Sat, 17 Oct 2026 16:24:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792254261; bh=c7vDTF6fv8pbNB8G4gLK129hxwk4tm/jjYBKVoXyaxA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LwwDKu9xWa+7gxSQBSGyKCuDCHXc8dohW2lsnKoe7tX8q7Mjc81297fh5YkqobZro ooreQexsQ14w1a0G6C8AVp3XkEio6HEhY0xV8KnkwMXEyOE3VGArAuvgmJuViXoQzD iqnr6fVTCY0phN0IlF47xM1XU8YzPCuTw9L6AqMQ= 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 6.12 390/869] cifs: prevent readdir from changing file size due to stale directory metadata Date: Sat, 17 Oct 2026 17:53:51 +0200 Message-ID: <20261017160047.116450528@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160036.979869304@linuxfoundation.org> References: <20261017160036.979869304@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 6.12-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 | 6 ++++ fs/smb/client/misc.c | 27 ++++++++++++++-- 5 files changed, 96 insertions(+), 9 deletions(-) diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c index 804a7e2f2c6d1..23ffe878dc3eb 100644 --- a/fs/smb/client/cifsfs.c +++ b/fs/smb/client/cifsfs.c @@ -434,6 +434,7 @@ cifs_alloc_inode(struct super_block *sb) return NULL; cifs_inode->cifsAttrs = 0x20; /* 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 697cdbd2d824e..0fbb3cd0daf5d 100644 --- a/fs/smb/client/cifsglob.h +++ b/fs/smb/client/cifsglob.h @@ -1535,6 +1535,7 @@ 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 ee3cc2b2fda41..0728858193bce 100644 --- a/fs/smb/client/file.c +++ b/fs/smb/client/file.c @@ -1325,11 +1325,21 @@ 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); } @@ -1358,6 +1368,10 @@ 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))) { @@ -3046,15 +3060,27 @@ 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->mnt_cifs_flags & CIFS_MOUNT_DIRECT_IO) { /* since no page cache to corrupt on directio we can change size safely */ @@ -3065,8 +3091,40 @@ 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 acb3220e5b703..db8a96e04e4d7 100644 --- a/fs/smb/client/inode.c +++ b/fs/smb/client/inode.c @@ -242,6 +242,8 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr, * calculating num blocks. */ inode->i_blocks = (512 - 1 + fattr->cf_bytes) >> 9; + } 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) { @@ -3188,6 +3190,8 @@ cifs_setattr_unix(struct dentry *direntry, struct iattr *attrs) if ((attrs->ia_valid & ATTR_SIZE) && attrs->ia_size != i_size_read(inode)) { + /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */ + smp_store_release(&cifsInode->time_last_write, jiffies); truncate_setsize(inode, attrs->ia_size); netfs_resize_file(&cifsInode->netfs, attrs->ia_size, true); fscache_resize_cookie(cifs_inode_cookie(inode), attrs->ia_size); @@ -3407,6 +3411,8 @@ cifs_setattr_nounix(struct dentry *direntry, struct iattr *attrs) if ((attrs->ia_valid & ATTR_SIZE) && attrs->ia_size != i_size_read(inode)) { + /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */ + smp_store_release(&cifsInode->time_last_write, jiffies); truncate_setsize(inode, attrs->ia_size); netfs_resize_file(&cifsInode->netfs, attrs->ia_size, true); fscache_resize_cookie(cifs_inode_cookie(inode), attrs->ia_size); diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c index 5ac8faeda4f7d..edfe24392bbdc 100644 --- a/fs/smb/client/misc.c +++ b/fs/smb/client/misc.c @@ -798,7 +798,14 @@ 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); } @@ -830,7 +837,14 @@ 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); } @@ -899,7 +913,14 @@ 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