Affected: Alpaquita:25: linux-lts, Alpaquita:stream: linux-lts

In the Linux kernel, the following vulnerability has been resolved:

net/smc: release the internal TCP sock on IPPROTO_SMC socket creation failure

IPPROTO_SMC sockets create an internal TCP sock ("clcsock") from the proto->init hook. When socket creation fails after proto->init has run - e.g. a cgroup BPF program attached to BPF_CGROUP_INET_SOCK_CREATE denies the socket - sk_common_release() only invokes sk_prot->destroy if it is set, but neither smc_inet_prot nor smc_inet6_prot defines it, and smc_destruct() returns early unless sk_state is SMC_CLOSED. As a result, every failing socket(AF_INET, SOCK_STREAM, IPPROTO_SMC) call leaks one tcp_sock, so an unprivileged task able to attach a deny-all BPF_CGROUP_INET_SOCK_CREATE program to its own cgroup can grow kernel memory unboundedly.

Add a .destroy hook to both protos that releases the clcsock via smc_clcsock_release(). smc_sk_init() hashes the sock into the smc hashinfo before the clcsock is created, and smc_diag dumps walk that hash dereferencing smc->clcsock without taking clcsock_release_lock, while sk_common_release() calls .destroy before .unhash. Unhash the sock before releasing the clcsock, as __smc_release() does, so a concurrent dump cannot observe the release; the second unhash in sk_common_release() is a no-op.

In the Linux kernel, the following vulnerability has been resolved:

net/smc: release the internal TCP sock on IPPROTO_SMC socket creation failure

IPPROTO_SMC sockets create an internal TCP sock ("clcsock") from the proto->init hook. When socket creation fails after proto->init has run - e.g. a cgroup BPF program attached to BPF_CGROUP_INET_SOCK_CREATE denies the socket - sk_common_release() only invokes sk_prot->destroy if it is set, but neither smc_inet_prot nor smc_inet6_prot defines it, and smc_destruct() returns early unless sk_state is SMC_CLOSED. As a result, every failing socket(AF_INET, SOCK_STREAM, IPPROTO_SMC) call leaks one tcp_sock, so an unprivileged task able to attach a deny-all BPF_CGROUP_INET_SOCK_CREATE program to its own cgroup can grow kernel memory unboundedly.

Add a .destroy hook to both protos that releases the clcsock via smc_clcsock_release(). smc_sk_init() hashes the sock into the smc hashinfo before the clcsock is created, and smc_diag dumps walk that hash dereferencing smc->clcsock without taking clcsock_release_lock, while sk_common_release() calls .destroy before .unhash. Unhash the sock before releasing the clcsock, as __smc_release() does, so a concurrent dump cannot observe the release; the second unhash in sk_common_release() is a no-op.

kernel-devel-7.2.7-1.1 on GA media

Affected: Ubuntu:16.04:LTS: linux-hwe-edge, Ubuntu:18.04:LTS: linux-aws-5.0, Ubuntu:18.04:LTS: linux-aws-5.3, Ubuntu:18.04:LTS: linux-azure, Ubuntu:18.04:LTS: linux-azure-5.3, Ubuntu:18.04:LTS: linux-azure-edge, Ubuntu:18.04:LTS: linux-gcp, Ubuntu:18.04:LTS: linux-gcp-5.3, Ubuntu:18.04:LTS: linux-gke-4.15, Ubuntu:18.04:LTS: linux-gke-5.4 and 120 more

In the Linux kernel, the following vulnerability has been resolved: net/smc: release the internal TCP sock on IPPROTO_SMC socket creation failure IPPROTO_SMC sockets create an internal TCP sock ("clcsock") from the proto->init hook. When socket creation fails after proto->init has run - e.g. a cgroup BPF program attached to BPF_CGROUP_INET_SOCK_CREATE denies the socket - sk_common_release() only invokes sk_prot->destroy if it is set, but neither smc_inet_prot nor smc_inet6_prot defines it, and smc_destruct() returns early unless sk_state is SMC_CLOSED. As a result, every failing socket(AF_INET, SOCK_STREAM, IPPROTO_SMC) call leaks one tcp_sock, so an unprivileged task able to attach a deny-all BPF_CGROUP_INET_SOCK_CREATE program to its own cgroup can grow kernel memory unboundedly. Add a .destroy hook to both protos that releases the clcsock via smc_clcsock_release(). smc_sk_init() hashes the sock into the smc hashinfo before the clcsock is created, and smc_diag dumps walk that hash dereferencing smc->clcsock without taking clcsock_release_lock, while sk_common_release() calls .destroy before .unhash. Unhash the sock before releasing the clcsock, as __smc_release() does, so a concurrent dump cannot observe the release; the second unhash in sk_common_release() is a no-op.