[PATCH v5 4/6] smb: client: clean up failed cached directory opens

[Zihan Xi]

open_cached_dir() sends CREATE and QUERY_INFO as a compound request. If
the CREATE succeeds but a later command returns an error, the function
must retain the CREATE FID so common cleanup can issue SMB2_close(). It
also must not treat a response error as a valid CREATE.

Validate the CREATE response before using its fields, record the FIDs, and
mark the handle open before handling errors from later compound commands.
Move the -EREMCHG reconnect handling before response validation so a
missing response does not hide the reconnect request. Count the handle
when it is marked open; confirmed close responses decrement the counter,
while existing close retry behavior remains best effort on transport
failures.

Fixes: b0f6df737a1c ("cifs: cache FILE_ALL_INFO for the shared root handle")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Vega <vega@xxxxxxxxxx>
Assisted-by: LLM
Co-developed-by: Luxing Yin <root@xxxxxxxxxx>
Signed-off-by: Luxing Yin <root@xxxxxxxxxx>
Signed-off-by: Zihan Xi <zihanx@xxxxxxxxxx>
---
changes in v5:
  - Rerolled the series after fixing a NULL dereference reported by the
    kernel test robot Smatch analysis in patch 5:
    https://lore.kernel.org/r/202609241449.HlHmnZFZ-lkp@xxxxxxxxx/
  - v4 Link: https://lore.kernel.org/all/cover.1789478666.git.zihanx@xxxxxxxxxx/
changes in v4:
  - Validate CREATE status and FIDs before marking the cached-directory handle
    open, preserve reconnect handling, and balance cleanup accounting.
  - Keep the cached-directory Fixes attribution at b0f6df737a1c.
  - v3 Link: https://lore.kernel.org/all/cover.1788516372.git.zihanx@xxxxxxxxxx/
changes in v3:
  - Split the POSIX handler check into a separate patch and corrected the
    parser Fixes history.
  - v2 Link: https://lore.kernel.org/all/cover.1787486936.git.zihanx@xxxxxxxxxx/
changes in v2:
  - Add cached-directory cleanup for failed compound opens.
  - v1 Link: https://lore.kernel.org/all/eb1bc35611f91bd10a4772400b37fac26f660956.1782579150.git.xizh2024@xxxxxxxxxx/

---
 fs/smb/client/cached_dir.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
index 88d5e9a32f28b..647fa26da4d24 100644
--- a/fs/smb/client/cached_dir.c
+++ b/fs/smb/client/cached_dir.c
@@ -8,6 +8,7 @@
 #include <linux/namei.h>
 #include "cifsglob.h"
 #include "cifsproto.h"
+#include "../common/smb2status.h"
 #include "cifs_debug.h"
 #include "smb2proto.h"
 #include "cached_dir.h"
@@ -323,25 +324,37 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 	rc = compound_send_recv(xid, ses, server,
 				flags, 2, rqst,
 				resp_buftype, rsp_iov);
-	if (rc) {
-		if (rc == -EREMCHG) {
-			tcon->need_reconnect = true;
-			pr_warn_once("server share %s deleted\n",
-				     tcon->tree_name);
-		}
-		goto oshr_free;
+	if (rc == -EREMCHG) {
+		tcon->need_reconnect = true;
+		pr_warn_once("server share %s deleted\n",
+			     tcon->tree_name);
 	}
-	cfid->is_open = true;
 
-	spin_lock(&cfids->cfid_list_lock);
+	if (!rsp_iov[0].iov_base || rsp_iov[0].iov_len < sizeof(*o_rsp)) {
+		if (!rc)
+			rc = -EIO;
+		goto oshr_free;
+	}
 
 	o_rsp = (struct smb2_create_rsp *)rsp_iov[0].iov_base;
+	if (o_rsp->hdr.Status != STATUS_SUCCESS) {
+		if (!rc)
+			rc = -EIO;
+		goto oshr_free;
+	}
+
 	oparms.fid->persistent_fid = o_rsp->PersistentFileId;
 	oparms.fid->volatile_fid = o_rsp->VolatileFileId;
 #ifdef CONFIG_CIFS_DEBUG2
 	oparms.fid->mid = le64_to_cpu(o_rsp->hdr.MessageId);
 #endif /* CIFS_DEBUG2 */
+	cfid->is_open = true;
+	atomic_inc(&tcon->num_remote_opens);
 
+	if (rc)
+		goto oshr_free;
+
+	spin_lock(&cfids->cfid_list_lock);
 
 	if (o_rsp->OplockLevel != SMB2_OPLOCK_LEVEL_LEASE) {
 		spin_unlock(&cfids->cfid_list_lock);
@@ -408,7 +421,6 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 		close_cached_dir(cfid);
 	} else {
 		*ret_cfid = cfid;
-		atomic_inc(&tcon->num_remote_opens);
 	}
 	kfree(utf16_path);
 
-- 
2.43.0