[PATCH] Fix segfault in smbXsrv_session_create()

[Andreas Schneider]

Hi,

the attached patch fixes a segfault in smbXsrv_session_create()

https://bugzilla.samba.org/show_bug.cgi?id=13315

The core dump I analyzed is from 4.6.2.

Review is very welcome!


Thanks,


	Andreas

-- 
Andreas Schneider                   GPG-ID: CC014E3D
Samba Team                             asn at samba.org
www.samba.org
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>From 9e869efa0073cf5be214d2d5e8bf9c37e5a80162 Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn at samba.org>
Date: Mon, 19 Feb 2018 18:07:50 +0100
Subject: [PATCH] s3:smbd: Do not crash if we fail to init the session table

This should the following segfault with SMB1:

  #6  sig_fault (sig=<optimized out>) at ../lib/util/fault.c:94
  #7  <signal handler called>
  #8  smbXsrv_session_create (conn=conn at entry=0x5654d3512af0, now=now at entry=131594481900356690, _session=_session at entry=0x7ffc93a778e8)
      at ../source3/smbd/smbXsrv_session.c:1212
  #9  0x00007f7618aa21ef in reply_sesssetup_and_X (req=req at entry=0x5654d35174b0) at ../source3/smbd/sesssetup.c:961
  #10 0x00007f7618ae17b0 in switch_message (type=<optimized out>, req=req at entry=0x5654d35174b0) at ../source3/smbd/process.c:1726
  #11 0x00007f7618ae3550 in construct_reply (deferred_pcd=0x0, encrypted=false, seqnum=0, unread_bytes=0, size=140, inbuf=0x0, xconn=0x5654d35146d0)
      at ../source3/smbd/process.c:1762
  #12 process_smb (xconn=xconn at entry=0x5654d3512af0, inbuf=<optimized out>, nread=140, unread_bytes=0, seqnum=0, encrypted=<optimized out>,
      deferred_pcd=deferred_pcd at entry=0x0) at ../source3/smbd/process.c:2008
  #13 0x00007f7618ae4c41 in smbd_server_connection_read_handler (xconn=0x5654d3512af0, fd=40) at ../source3/smbd/process.c:2608
  #14 0x00007f761587eedb in epoll_event_loop_once () from /lib64/libtevent.so.0

Inspection the core shows that:
  conn->client-session_table is NULL
  conn->protocol is PROTOCOL_NONE

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13315

Signed-off-by: Andreas Schneider <asn at samba.org>
---
 source3/smbd/negprot.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/source3/smbd/negprot.c b/source3/smbd/negprot.c
index 3a9363d528b..a36822e1907 100644
--- a/source3/smbd/negprot.c
+++ b/source3/smbd/negprot.c
@@ -65,6 +65,8 @@ static void reply_lanman1(struct smb_request *req, uint16_t choice)
 	time_t t = time(NULL);
 	struct smbXsrv_connection *xconn = req->xconn;
 	uint16_t raw;
+	NTSTATUS status;
+
 	if (lp_async_smb_echo_handler()) {
 		raw = 0;
 	} else {
@@ -88,7 +90,11 @@ static void reply_lanman1(struct smb_request *req, uint16_t choice)
 		SSVAL(req->outbuf,smb_vwv11, 8);
 	}
 
-	smbXsrv_connection_init_tables(xconn, PROTOCOL_LANMAN1);
+	status = smbXsrv_connection_init_tables(xconn, PROTOCOL_LANMAN1);
+	if (!NT_STATUS_IS_OK(status)) {
+		reply_nterror(req, status);
+		return;
+	}
 
 	/* Reply, SMBlockread, SMBwritelock supported. */
 	SCVAL(req->outbuf,smb_flg, FLAG_REPLY|FLAG_SUPPORT_LOCKREAD);
@@ -115,6 +121,8 @@ static void reply_lanman2(struct smb_request *req, uint16_t choice)
 	time_t t = time(NULL);
 	struct smbXsrv_connection *xconn = req->xconn;
 	uint16_t raw;
+	NTSTATUS status;
+
 	if (lp_async_smb_echo_handler()) {
 		raw = 0;
 	} else {
@@ -140,7 +148,11 @@ static void reply_lanman2(struct smb_request *req, uint16_t choice)
 		SSVAL(req->outbuf,smb_vwv11, 8);
 	}
 
-	smbXsrv_connection_init_tables(xconn, PROTOCOL_LANMAN2);
+	status = smbXsrv_connection_init_tables(xconn, PROTOCOL_LANMAN2);
+	if (!NT_STATUS_IS_OK(status)) {
+		reply_nterror(req, status);
+		return;
+	}
 
 	/* Reply, SMBlockread, SMBwritelock supported. */
 	SCVAL(req->outbuf,smb_flg,FLAG_REPLY|FLAG_SUPPORT_LOCKREAD);
@@ -260,6 +272,7 @@ static void reply_nt1(struct smb_request *req, uint16_t choice)
 	struct smbXsrv_connection *xconn = req->xconn;
 	bool signing_desired = false;
 	bool signing_required = false;
+	NTSTATUS status;
 
 	xconn->smb1.negprot.encrypted_passwords = lp_encrypt_passwords();
 
@@ -336,7 +349,11 @@ static void reply_nt1(struct smb_request *req, uint16_t choice)
 	SSVAL(req->outbuf,smb_vwv0,choice);
 	SCVAL(req->outbuf,smb_vwv1,secword);
 
-	smbXsrv_connection_init_tables(xconn, PROTOCOL_NT1);
+	status = smbXsrv_connection_init_tables(xconn, PROTOCOL_NT1);
+	if (!NT_STATUS_IS_OK(status)) {
+		reply_nterror(req, status);
+		return;
+	}
 
 	SSVAL(req->outbuf,smb_vwv1+1, lp_max_mux()); /* maxmpx */
 	SSVAL(req->outbuf,smb_vwv2+1, 1); /* num vcs */
-- 
2.16.2