linux-kernel - [PATCH v4] ksmbd: fix possible memory leak in smb2

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Message-Id: <20230214063650.12832-1-hbh25y@gmail.com>
Date:   Tue, 14 Feb 2023 14:36:50 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     linkinjeon@...nel.org, sfrench@...ba.org, senozhatsky@...omium.org,
        tom@...pey.com, hyc.lee@...il.com, lsahlber@...hat.com
Cc:     linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hangyu Hua <hbh25y@...il.com>
Subject: [PATCH v4] 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

 fs/ksmbd/smb2pdu.c   | 20 +++++++++++++-------
 fs/ksmbd/vfs_cache.c |  2 ++
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index d681f91947d9..1b517d3ca2ef 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -6666,7 +6666,8 @@ 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;
+			if (iter->cancel_fn)
+				cancel_work = iter;
 			break;
 		}
 		spin_unlock(&conn->request_lock);
@@ -7050,6 +7051,7 @@ int smb2_lock(struct ksmbd_work *work)
 						      smb2_remove_blocked_lock,
 						      argv);
 				if (rc) {
+					kfree(argv);
 					err = -ENOMEM;
 					goto out;
 				}
@@ -7061,6 +7063,16 @@ int smb2_lock(struct ksmbd_work *work)
 
 				ksmbd_vfs_posix_lock_wait(flock);
 
+				spin_lock(&work->conn->request_lock);
+				spin_lock(&fp->f_lock);
+				if (work->state != KSMBD_WORK_CLOSED) {
+					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 +7081,6 @@ 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 +7102,6 @@ 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..761a8aa540ce 100644
--- a/fs/ksmbd/vfs_cache.c
+++ b/fs/ksmbd/vfs_cache.c
@@ -372,6 +372,8 @@ static void set_close_state_blocked_works(struct ksmbd_file *fp)
 		list_del(&cancel_work->fp_entry);
 		cancel_work->state = KSMBD_WORK_CLOSED;
 		cancel_work->cancel_fn(cancel_work->cancel_argv);
+		cancel_work->cancel_fn = NULL;
+		kfree(cancel_work->cancel_argv);
 	}
 	spin_unlock(&fp->f_lock);
 }
-- 
2.34.1