* [PATCH v4 1/2] cifs: prevent readdir from changing file size due to stale directory metadata
2026-07-21 23:55 [PATCH v4 0/2] cifs: fix readdir stale size bug and deferred-close reference leak Frank Sorenson
@ 2026-07-21 23:55 ` Frank Sorenson
2026-07-21 23:55 ` [PATCH v4 2/2] cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths Frank Sorenson
2026-07-22 1:28 ` [PATCH v4 0/2] cifs: fix readdir stale size bug and deferred-close reference leak Steve French
2 siblings, 0 replies; 4+ messages in thread
From: Frank Sorenson @ 2026-07-21 23:55 UTC (permalink / raw)
To: linux-cifs, pc, stfrench
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 <sorenson@redhat.com>
---
diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index 66b9104e7ca2..1788d93a2522 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -440,6 +440,7 @@ 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 08e94633a9c1..79e4e84f8985 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1566,6 +1566,7 @@ 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 968740e7c9c3..b279a44be729 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -1423,11 +1423,21 @@ 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);
}
@@ -1457,6 +1467,10 @@ 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_obj(struct cifs_deferred_close);
if ((cfile->status_file_deleted == false) &&
(smb2_can_defer_close(inode, dclose))) {
@@ -3225,13 +3239,26 @@ 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);
+
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(cifsInode);
+
+ /*
+ * 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
@@ -3243,8 +3270,40 @@ 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 deed04dd9b91..b2806371bfde 100644
--- a/fs/smb/client/inode.c
+++ b/fs/smb/client/inode.c
@@ -237,6 +237,8 @@ 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) {
@@ -3277,6 +3279,8 @@ 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);
@@ -3478,6 +3482,8 @@ 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 e4bac2a0b85d..0301ca932ce9 100644
--- a/fs/smb/client/misc.c
+++ b/fs/smb/client/misc.c
@@ -524,7 +524,14 @@ 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);
}
@@ -557,7 +564,14 @@ 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);
}
@@ -626,7 +640,14 @@ 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);
}
---
2.55.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v4 2/2] cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths
2026-07-21 23:55 [PATCH v4 0/2] cifs: fix readdir stale size bug and deferred-close reference leak Frank Sorenson
2026-07-21 23:55 ` [PATCH v4 1/2] cifs: prevent readdir from changing file size due to stale directory metadata Frank Sorenson
@ 2026-07-21 23:55 ` Frank Sorenson
2026-07-22 1:28 ` [PATCH v4 0/2] cifs: fix readdir stale size bug and deferred-close reference leak Steve French
2 siblings, 0 replies; 4+ messages in thread
From: Frank Sorenson @ 2026-07-21 23:55 UTC (permalink / raw)
To: linux-cifs, pc, stfrench
In cifs_close_deferred_file(), cifs_close_all_deferred_files(), and
cifs_close_deferred_file_under_dentry(), when a pending deferred close
is cancelled via cancel_delayed_work(), the subsequent kmalloc_obj() to
add the file to the local processing list may fail under memory pressure.
The loop breaks immediately, but the cancelled work is no longer pending
(it would have called _cifsFileInfo_put()), and the cfile is never added
to file_head for processing. The cifsFileInfo reference and the open
server handle both leak.
Fix by saving the cfile that failed allocation in a local variable,
breaking as before, and calling _cifsFileInfo_put() on it after
releasing the lock. Any files later in the iteration are unaffected
since their deferred work is still pending and will fire normally.
Fixes: e3fc065682eb ("cifs: Deferred close performance improvements")
Signed-off-by: Frank Sorenson <sorenson@redhat.com>
---
--- a/fs/smb/client/misc.c
+++ b/fs/smb/client/misc.c
@@ -497,7 +497,7 @@
void
cifs_close_deferred_file(struct cifsInodeInfo *cifs_inode)
{
- struct cifsFileInfo *cfile = NULL;
+ struct cifsFileInfo *cfile = NULL, *failed_cfile = NULL;
struct file_list *tmp_list, *tmp_next_list;
LIST_HEAD(file_head);
@@ -514,8 +514,10 @@
tmp_list = kmalloc_obj(struct file_list,
GFP_ATOMIC);
- if (tmp_list == NULL)
+ if (tmp_list == NULL) {
+ failed_cfile = cfile;
break;
+ }
tmp_list->cfile = cfile;
list_add_tail(&tmp_list->list, &file_head);
}
@@ -523,6 +525,15 @@
}
spin_unlock(&cifs_inode->open_file_lock);
+ if (failed_cfile) {
+ if (OPEN_FMODE(failed_cfile->f_flags) & FMODE_WRITE) {
+ /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */
+ smp_store_release(&CIFS_I(d_inode(failed_cfile->dentry))->time_last_write,
+ jiffies);
+ }
+ _cifsFileInfo_put(failed_cfile, false, false);
+ }
+
list_for_each_entry_safe(tmp_list, tmp_next_list, &file_head, list) {
struct cifsFileInfo *cfile = tmp_list->cfile;
@@ -540,7 +551,7 @@
void
cifs_close_all_deferred_files(struct cifs_tcon *tcon)
{
- struct cifsFileInfo *cfile;
+ struct cifsFileInfo *cfile, *failed_cfile = NULL;
struct file_list *tmp_list, *tmp_next_list;
LIST_HEAD(file_head);
@@ -554,8 +565,10 @@
tmp_list = kmalloc_obj(struct file_list,
GFP_ATOMIC);
- if (tmp_list == NULL)
+ if (tmp_list == NULL) {
+ failed_cfile = cfile;
break;
+ }
tmp_list->cfile = cfile;
list_add_tail(&tmp_list->list, &file_head);
}
@@ -563,6 +576,15 @@
}
spin_unlock(&tcon->open_file_lock);
+ if (failed_cfile) {
+ if (OPEN_FMODE(failed_cfile->f_flags) & FMODE_WRITE) {
+ /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */
+ smp_store_release(&CIFS_I(d_inode(failed_cfile->dentry))->time_last_write,
+ jiffies);
+ }
+ _cifsFileInfo_put(failed_cfile, true, false);
+ }
+
list_for_each_entry_safe(tmp_list, tmp_next_list, &file_head, list) {
struct cifsFileInfo *cfile = tmp_list->cfile;
@@ -618,7 +640,7 @@
struct dentry *dentry)
{
struct file_list *tmp_list, *tmp_next_list;
- struct cifsFileInfo *cfile;
+ struct cifsFileInfo *cfile, *failed_cfile = NULL;
LIST_HEAD(file_head);
spin_lock(&tcon->open_file_lock);
@@ -631,14 +653,25 @@
spin_unlock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock);
tmp_list = kmalloc_obj(struct file_list, GFP_ATOMIC);
- if (tmp_list == NULL)
+ if (tmp_list == NULL) {
+ failed_cfile = cfile;
break;
+ }
tmp_list->cfile = cfile;
list_add_tail(&tmp_list->list, &file_head);
}
}
spin_unlock(&tcon->open_file_lock);
+ if (failed_cfile) {
+ if (OPEN_FMODE(failed_cfile->f_flags) & FMODE_WRITE) {
+ /* Pairs with smp_load_acquire() in is_size_safe_to_change(). */
+ smp_store_release(&CIFS_I(d_inode(failed_cfile->dentry))->time_last_write,
+ jiffies);
+ }
+ _cifsFileInfo_put(failed_cfile, true, false);
+ }
+
list_for_each_entry_safe(tmp_list, tmp_next_list, &file_head, list) {
struct cifsFileInfo *cfile = tmp_list->cfile;
---
2.55.0
^ permalink raw reply [flat|nested] 4+ messages in thread