linux-kernel - [PATCH] cifsd: Fix a use after free on error path

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Message-ID: <YFNR1sVU2mIgxNma@mwanda>
Date:   Thu, 18 Mar 2021 16:12:54 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Namjae Jeon <namjae.jeon@...sung.com>
Cc:     Hyunchul Lee <hyc.lee@...il.com>,
        Steve French <stfrench@...rosoft.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Ronnie Sahlberg <lsahlber@...hat.com>,
        linux-kernel@...r.kernel.org, linux-cifs@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] cifsd: Fix a use after free on error path

The ksmbd_free_work_struct() frees "work" so we need to swap the order
of these two function calls to avoid a use after free.

Fixes: cabcebc31de4 ("cifsd: introduce SMB3 kernel server")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 fs/cifsd/oplock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/cifsd/oplock.c b/fs/cifsd/oplock.c
index 6c3dbc71134e..f694c14be0df 100644
--- a/fs/cifsd/oplock.c
+++ b/fs/cifsd/oplock.c
@@ -638,8 +638,8 @@ static void __smb2_oplock_break_noti(struct work_struct *wk)
 	if (allocate_oplock_break_buf(work)) {
 		ksmbd_err("smb2_allocate_rsp_buf failed! ");
 		atomic_dec(&conn->r_count);
-		ksmbd_free_work_struct(work);
 		ksmbd_fd_put(work, fp);
+		ksmbd_free_work_struct(work);
 		return;
 	}
 
-- 
2.30.2