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Commit 5fb4e288 authored by Christopher Oo's avatar Christopher Oo Committed by Steve French
Browse files

cifs: Fix use-after-free on mid_q_entry 



With CIFS_DEBUG_2 enabled, additional debug information is tracked inside each
mid_q_entry struct, however cifs_save_when_sent may use the mid_q_entry after it
has been freed from the appropriate callback if the transport layer has very low
latency. Holding the srv_mutex fixes this use-after-free, as cifs_save_when_sent
is called while the srv_mutex is held while the request is sent.

Signed-off-by: default avatarChristopher Oo <t-chriso@microsoft.com>
parent 0a6d0b64

fs/cifs/cifssmb.c

+7 −0
Original line number Diff line number Diff line
@@ -696,7 +696,9 @@ cifs_echo_callback(struct mid_q_entry *mid) 
{

	struct TCP_Server_Info *server = mid->callback_data;



	mutex_lock(&server->srv_mutex);

	DeleteMidQEntry(mid);

	mutex_unlock(&server->srv_mutex);

	add_credits(server, 1, CIFS_ECHO_OP);

}
@@ -1572,7 +1574,9 @@ cifs_readv_callback(struct mid_q_entry *mid) 
	}



	queue_work(cifsiod_wq, &rdata->work);

	mutex_lock(&server->srv_mutex);

	DeleteMidQEntry(mid);

	mutex_unlock(&server->srv_mutex);

	add_credits(server, 1, 0);

}
@@ -2032,6 +2036,7 @@ cifs_writev_callback(struct mid_q_entry *mid) 
{

	struct cifs_writedata *wdata = mid->callback_data;

	struct cifs_tcon *tcon = tlink_tcon(wdata->cfile->tlink);

	struct TCP_Server_Info *server = tcon->ses->server;

	unsigned int written;

	WRITE_RSP *smb = (WRITE_RSP *)mid->resp_buf;
@@ -2068,7 +2073,9 @@ cifs_writev_callback(struct mid_q_entry *mid) 
	}



	queue_work(cifsiod_wq, &wdata->work);

	mutex_lock(&server->srv_mutex);

	DeleteMidQEntry(mid);

	mutex_unlock(&server->srv_mutex);

	add_credits(tcon->ses->server, 1, 0);

}

fs/cifs/smb2pdu.c

+7 −0
Original line number Diff line number Diff line
@@ -1626,7 +1626,9 @@ smb2_echo_callback(struct mid_q_entry *mid) 
	if (mid->mid_state == MID_RESPONSE_RECEIVED)

		credits_received = le16_to_cpu(smb2->hdr.CreditRequest);



	mutex_lock(&server->srv_mutex);

	DeleteMidQEntry(mid);

	mutex_unlock(&server->srv_mutex);

	add_credits(server, credits_received, CIFS_ECHO_OP);

}
@@ -1810,7 +1812,9 @@ smb2_readv_callback(struct mid_q_entry *mid) 
		cifs_stats_fail_inc(tcon, SMB2_READ_HE);



	queue_work(cifsiod_wq, &rdata->work);

	mutex_lock(&server->srv_mutex);

	DeleteMidQEntry(mid);

	mutex_unlock(&server->srv_mutex);

	add_credits(server, credits_received, 0);

}
@@ -1938,6 +1942,7 @@ smb2_writev_callback(struct mid_q_entry *mid) 
{

	struct cifs_writedata *wdata = mid->callback_data;

	struct cifs_tcon *tcon = tlink_tcon(wdata->cfile->tlink);

	struct TCP_Server_Info *server = tcon->ses->server;

	unsigned int written;

	struct smb2_write_rsp *rsp = (struct smb2_write_rsp *)mid->resp_buf;

	unsigned int credits_received = 1;
@@ -1977,7 +1982,9 @@ smb2_writev_callback(struct mid_q_entry *mid) 
		cifs_stats_fail_inc(tcon, SMB2_WRITE_HE);



	queue_work(cifsiod_wq, &wdata->work);

	mutex_lock(&server->srv_mutex);

	DeleteMidQEntry(mid);

	mutex_unlock(&server->srv_mutex);

	add_credits(tcon->ses->server, credits_received, 0);

}

fs/cifs/transport.c

+2 −0
Original line number Diff line number Diff line
@@ -644,7 +644,9 @@ cifs_sync_mid_result(struct mid_q_entry *mid, struct TCP_Server_Info *server) 
	}

	spin_unlock(&GlobalMid_Lock);



	mutex_lock(&server->srv_mutex);

	DeleteMidQEntry(mid);

	mutex_unlock(&server->srv_mutex);

	return rc;

}