linux-kernel - [PATCH][V2] cifs: fix memory leak of an allocated cifs

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Message-Id: <20190116162859.8028-1-colin.king@canonical.com>
Date:   Wed, 16 Jan 2019 16:28:59 +0000
From:   Colin King <colin.king@...onical.com>
To:     Steve French <sfrench@...ba.org>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][V2] cifs: fix memory leak of an allocated cifs_ntsd structure

From: Colin Ian King <colin.king@...onical.com>

The call to SMB2_queary_acl can allocate memory to pntsd and also
return a failure via a call to SMB2_query_acl (and then query_info).
This occurs when query_info allocates the structure and then in
query_info the call to smb2_validate_and_copy_iov fails. Currently the
failure just returns without kfree'ing pntsd hence causing a memory
leak.

Currently, *data is allocated if it's not already pointing to a buffer,
so it needs to be kfree'd only if was allocated in query_info, so the
fix adds an allocated flag to track this.  Also set *dlen to zero on
an error just to be safe since *data is kfree'd.

Also set errno to -ENOMEM if the allocation of *data fails.

Signed-off-by: Colin Ian King <colin.king@...onical.com>

---
 fs/cifs/smb2pdu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 50811a7dc0e0..0af87bd0dc49 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -2816,6 +2816,7 @@ query_info(const unsigned int xid, struct cifs_tcon *tcon,
 	int resp_buftype = CIFS_NO_BUFFER;
 	struct cifs_ses *ses = tcon->ses;
 	int flags = 0;
+	bool allocated = false;

 	cifs_dbg(FYI, "Query Info\n");

@@ -2855,14 +2856,21 @@ query_info(const unsigned int xid, struct cifs_tcon *tcon,
 					"Error %d allocating memory for acl\n",
 					rc);
 				*dlen = 0;
+				rc = -ENOMEM;
 				goto qinf_exit;
 			}
+			allocated = true;
 		}
 	}

 	rc = smb2_validate_and_copy_iov(le16_to_cpu(rsp->OutputBufferOffset),
 					le32_to_cpu(rsp->OutputBufferLength),
 					&rsp_iov, min_len, *data);
+	if (rc && allocated) {
+		kfree(*data);
+		*data = NULL;
+		*dlen = 0;
+	}

 qinf_exit:
 	SMB2_query_info_free(&rqst);
-- 
2.19.1