[PATCH 4.19-stable 3/3] tcp: add sanity tests to TCP_QUEUE_SEQ

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

[ Upstream commit 8811f4a9836e31c14ecdf79d9f3cb7c5d463265d ]

Qingyu Li reported a syzkaller bug where the repro
changes RCV SEQ _after_ restoring data in the receive queue.

mprotect(0x4aa000, 12288, PROT_READ)    = 0
mmap(0x1ffff000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 
0x1ffff000
mmap(0x20000000, 16777216, PROT_READ|PROT_WRITE|PROT_EXEC, 
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x20000000
mmap(0x21000000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 
0x21000000
socket(AF_INET6, SOCK_STREAM, IPPROTO_IP) = 3
setsockopt(3, SOL_TCP, TCP_REPAIR, [1], 4) = 0
connect(3, {sa_family=AF_INET6, sin6_port=htons(0), sin6_flowinfo=htonl(0), 
inet_pton(AF_INET6, "::1", &sin6_addr), sin6_scope_id=0}, 28) = 0
setsockopt(3, SOL_TCP, TCP_REPAIR_QUEUE, [1], 4) = 0
sendmsg(3, {msg_name=NULL, msg_namelen=0, 
msg_iov=[{iov_base="0x0000000000000003\0\0", iov_len=20}], msg_iovlen=1, 
msg_controllen=0, msg_flags=0}, 0) = 20
setsockopt(3, SOL_TCP, TCP_REPAIR, [0], 4) = 0
setsockopt(3, SOL_TCP, TCP_QUEUE_SEQ, [128], 4) = 0
recvfrom(3, NULL, 20, 0, NULL, NULL)    = -1 ECONNRESET (Connection reset by 
peer)

syslog shows:
[  111.205099] TCP recvmsg seq # bug 2: copied 80, seq 0, rcvnxt 80, fl 0
[  111.207894] WARNING: CPU: 1 PID: 356 at net/ipv4/tcp.c:2343 
tcp_recvmsg_locked+0x90e/0x29a0

This should not be allowed. TCP_QUEUE_SEQ should only be used
when queues are empty.

This patch fixes this case, and the tx path as well.

Fixes: ee9952831cfd ("tcp: Initial repair mode")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Pavel Emelyanov <xe...@parallels.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=212005
Reported-by: Qingyu Li <ieatmuttonch...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
---
 net/ipv4/tcp.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 
370faff782cd363e82014969331df459b8188d94..769e1f683471ace151855df8c682c1b784cc59f7
 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2886,16 +2886,23 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
                break;
 
        case TCP_QUEUE_SEQ:
-               if (sk->sk_state != TCP_CLOSE)
+               if (sk->sk_state != TCP_CLOSE) {
                        err = -EPERM;
-               else if (tp->repair_queue == TCP_SEND_QUEUE)
-                       WRITE_ONCE(tp->write_seq, val);
-               else if (tp->repair_queue == TCP_RECV_QUEUE) {
-                       WRITE_ONCE(tp->rcv_nxt, val);
-                       WRITE_ONCE(tp->copied_seq, val);
-               }
-               else
+               } else if (tp->repair_queue == TCP_SEND_QUEUE) {
+                       if (!tcp_rtx_queue_empty(sk))
+                               err = -EPERM;
+                       else
+                               WRITE_ONCE(tp->write_seq, val);
+               } else if (tp->repair_queue == TCP_RECV_QUEUE) {
+                       if (tp->rcv_nxt != tp->copied_seq) {
+                               err = -EPERM;
+                       } else {
+                               WRITE_ONCE(tp->rcv_nxt, val);
+                               WRITE_ONCE(tp->copied_seq, val);
+                       }
+               } else {
                        err = -EINVAL;
+               }
                break;
 
        case TCP_REPAIR_OPTIONS:
-- 
2.31.0.rc2.261.g7f71774620-goog