linux-kernel - [PATCH v5] ksmbd: fix possible memory leak in smb2

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Message-Id: <20230215083350.5815-1-hbh25y@gmail.com>
Date:   Wed, 15 Feb 2023 16:33:50 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     linkinjeon@...nel.org, sfrench@...ba.org, senozhatsky@...omium.org,
        tom@...pey.com, lsahlber@...hat.com, hyc.lee@...il.com
Cc:     linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hangyu Hua <hbh25y@...il.com>
Subject: [PATCH v5] ksmbd: fix possible memory leak in smb2_lock()

argv needs to be free when setup_async_work fails or when the current
process is woken up.

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Hangyu Hua <hbh25y@...il.com>
---

v2: avoid NULL pointer dereference in set_close_state_blocked_works().
v3: avoid race condition between smb2_lock() and smb2_cancel().
v4: use another way to avoid race condition.
v5: Keep things under the control of request_lock and f_lock.

 fs/ksmbd/smb2pdu.c   | 28 +++++++++++++---------------
 fs/ksmbd/vfs_cache.c |  5 ++---
 2 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index d681f91947d9..875eecc6b95e 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -6644,7 +6644,7 @@ int smb2_cancel(struct ksmbd_work *work)
 	struct ksmbd_conn *conn = work->conn;
 	struct smb2_hdr *hdr = smb2_get_msg(work->request_buf);
 	struct smb2_hdr *chdr;
-	struct ksmbd_work *cancel_work = NULL, *iter;
+	struct ksmbd_work *iter;
 	struct list_head *command_list;
 
 	ksmbd_debug(SMB, "smb2 cancel called on mid %llu, async flags 0x%x\n",
@@ -6666,7 +6666,9 @@ int smb2_cancel(struct ksmbd_work *work)
 				    "smb2 with AsyncId %llu cancelled command = 0x%x\n",
 				    le64_to_cpu(hdr->Id.AsyncId),
 				    le16_to_cpu(chdr->Command));
-			cancel_work = iter;
+			iter->state = KSMBD_WORK_CANCELLED;
+			if (iter->cancel_fn)
+				iter->cancel_fn(iter->cancel_argv);
 			break;
 		}
 		spin_unlock(&conn->request_lock);
@@ -6685,18 +6687,12 @@ int smb2_cancel(struct ksmbd_work *work)
 				    "smb2 with mid %llu cancelled command = 0x%x\n",
 				    le64_to_cpu(hdr->MessageId),
 				    le16_to_cpu(chdr->Command));
-			cancel_work = iter;
+			iter->state = KSMBD_WORK_CANCELLED;
 			break;
 		}
 		spin_unlock(&conn->request_lock);
 	}
 
-	if (cancel_work) {
-		cancel_work->state = KSMBD_WORK_CANCELLED;
-		if (cancel_work->cancel_fn)
-			cancel_work->cancel_fn(cancel_work->cancel_argv);
-	}
-
 	/* For SMB2_CANCEL command itself send no response*/
 	work->send_no_response = 1;
 	return 0;
@@ -7061,6 +7057,14 @@ int smb2_lock(struct ksmbd_work *work)
 
 				ksmbd_vfs_posix_lock_wait(flock);
 
+				spin_lock(&work->conn->request_lock);
+				spin_lock(&fp->f_lock);
+				list_del(&work->fp_entry);
+				work->cancel_fn = NULL;
+				kfree(argv);
+				spin_unlock(&fp->f_lock);
+				spin_unlock(&work->conn->request_lock);
+
 				if (work->state != KSMBD_WORK_ACTIVE) {
 					list_del(&smb_lock->llist);
 					spin_lock(&work->conn->llist_lock);
@@ -7069,9 +7073,6 @@ int smb2_lock(struct ksmbd_work *work)
 					locks_free_lock(flock);
 
 					if (work->state == KSMBD_WORK_CANCELLED) {
-						spin_lock(&fp->f_lock);
-						list_del(&work->fp_entry);
-						spin_unlock(&fp->f_lock);
 						rsp->hdr.Status =
 							STATUS_CANCELLED;
 						kfree(smb_lock);
@@ -7093,9 +7094,6 @@ int smb2_lock(struct ksmbd_work *work)
 				list_del(&smb_lock->clist);
 				spin_unlock(&work->conn->llist_lock);
 
-				spin_lock(&fp->f_lock);
-				list_del(&work->fp_entry);
-				spin_unlock(&fp->f_lock);
 				goto retry;
 			} else if (!rc) {
 				spin_lock(&work->conn->llist_lock);
diff --git a/fs/ksmbd/vfs_cache.c b/fs/ksmbd/vfs_cache.c
index da9163b00350..0ae5dd0829e9 100644
--- a/fs/ksmbd/vfs_cache.c
+++ b/fs/ksmbd/vfs_cache.c
@@ -364,12 +364,11 @@ static void __put_fd_final(struct ksmbd_work *work, struct ksmbd_file *fp)
 
 static void set_close_state_blocked_works(struct ksmbd_file *fp)
 {
-	struct ksmbd_work *cancel_work, *ctmp;
+	struct ksmbd_work *cancel_work;
 
 	spin_lock(&fp->f_lock);
-	list_for_each_entry_safe(cancel_work, ctmp, &fp->blocked_works,
+	list_for_each_entry(cancel_work, &fp->blocked_works,
 				 fp_entry) {
-		list_del(&cancel_work->fp_entry);
 		cancel_work->state = KSMBD_WORK_CLOSED;
 		cancel_work->cancel_fn(cancel_work->cancel_argv);
 	}
-- 
2.34.1