6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michal Luczaj mhal@rbox.co
[ Upstream commit 687aa0c5581b8d4aa87fd92973e4ee576b550cdf ]
Transport assignment may race with module unload. Protect new_transport from becoming a stale pointer.
This also takes care of an insecure call in vsock_use_local_transport(); add a lockdep assert.
BUG: unable to handle page fault for address: fffffbfff8056000 Oops: Oops: 0000 [#1] SMP KASAN RIP: 0010:vsock_assign_transport+0x366/0x600 Call Trace: vsock_connect+0x59c/0xc40 __sys_connect+0xe8/0x100 __x64_sys_connect+0x6e/0xc0 do_syscall_64+0x92/0x1c0 entry_SYSCALL_64_after_hwframe+0x4b/0x53
Fixes: c0cfa2d8a788 ("vsock: add multi-transports support") Reviewed-by: Stefano Garzarella sgarzare@redhat.com Signed-off-by: Michal Luczaj mhal@rbox.co Link: https://patch.msgid.link/20250703-vsock-transports-toctou-v4-2-98f0eb530747@... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/vmw_vsock/af_vsock.c | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-)
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index f671f2375f04b..108e4cef7edd5 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -407,6 +407,8 @@ EXPORT_SYMBOL_GPL(vsock_enqueue_accept);
static bool vsock_use_local_transport(unsigned int remote_cid) { + lockdep_assert_held(&vsock_register_mutex); + if (!transport_local) return false;
@@ -464,6 +466,8 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
remote_flags = vsk->remote_addr.svm_flags;
+ mutex_lock(&vsock_register_mutex); + switch (sk->sk_type) { case SOCK_DGRAM: new_transport = transport_dgram; @@ -479,12 +483,15 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk) new_transport = transport_h2g; break; default: - return -ESOCKTNOSUPPORT; + ret = -ESOCKTNOSUPPORT; + goto err; }
if (vsk->transport) { - if (vsk->transport == new_transport) - return 0; + if (vsk->transport == new_transport) { + ret = 0; + goto err; + }
/* transport->release() must be called with sock lock acquired. * This path can only be taken during vsock_connect(), where we @@ -508,8 +515,16 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk) /* We increase the module refcnt to prevent the transport unloading * while there are open sockets assigned to it. */ - if (!new_transport || !try_module_get(new_transport->module)) - return -ENODEV; + if (!new_transport || !try_module_get(new_transport->module)) { + ret = -ENODEV; + goto err; + } + + /* It's safe to release the mutex after a successful try_module_get(). + * Whichever transport `new_transport` points at, it won't go away until + * the last module_put() below or in vsock_deassign_transport(). + */ + mutex_unlock(&vsock_register_mutex);
if (sk->sk_type == SOCK_SEQPACKET) { if (!new_transport->seqpacket_allow || @@ -528,6 +543,9 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk) vsk->transport = new_transport;
return 0; +err: + mutex_unlock(&vsock_register_mutex); + return ret; } EXPORT_SYMBOL_GPL(vsock_assign_transport);