CVE-2021-4442

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> tcp: add sanity tests to TCP_QUEUE_SEQ<br /> <br /> Qingyu Li reported a syzkaller bug where the repro<br /> changes RCV SEQ _after_ restoring data in the receive queue.<br /> <br /> mprotect(0x4aa000, 12288, PROT_READ) = 0<br /> mmap(0x1ffff000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x1ffff000<br /> mmap(0x20000000, 16777216, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x20000000<br /> mmap(0x21000000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x21000000<br /> socket(AF_INET6, SOCK_STREAM, IPPROTO_IP) = 3<br /> setsockopt(3, SOL_TCP, TCP_REPAIR, [1], 4) = 0<br /> connect(3, {sa_family=AF_INET6, sin6_port=htons(0), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "::1", &amp;sin6_addr), sin6_scope_id=0}, 28) = 0<br /> setsockopt(3, SOL_TCP, TCP_REPAIR_QUEUE, [1], 4) = 0<br /> 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<br /> setsockopt(3, SOL_TCP, TCP_REPAIR, [0], 4) = 0<br /> setsockopt(3, SOL_TCP, TCP_QUEUE_SEQ, [128], 4) = 0<br /> recvfrom(3, NULL, 20, 0, NULL, NULL) = -1 ECONNRESET (Connection reset by peer)<br /> <br /> syslog shows:<br /> [ 111.205099] TCP recvmsg seq # bug 2: copied 80, seq 0, rcvnxt 80, fl 0<br /> [ 111.207894] WARNING: CPU: 1 PID: 356 at net/ipv4/tcp.c:2343 tcp_recvmsg_locked+0x90e/0x29a0<br /> <br /> This should not be allowed. TCP_QUEUE_SEQ should only be used<br /> when queues are empty.<br /> <br /> This patch fixes this case, and the tx path as well.