This command is used to identify the commands/events supported by the introspection subsystem and it is always allowed. Any attempt from userspace to explicitly disallow this command through the KVM_INTROSPECTION_COMMAND ioctl will get -EPERM, unless userspace disables all commands, using id=-1, in which case KVMI_GET_VERSION is silently allowed, without error.
Signed-off-by: Adalbert Lazăr <[email protected]> --- Documentation/virt/kvm/kvmi.rst | 35 +++++++++++++++++++ include/uapi/linux/kvmi.h | 10 ++++++ .../testing/selftests/kvm/x86_64/kvmi_test.c | 25 +++++++++++++ virt/kvm/introspection/kvmi.c | 27 +++++++++++--- virt/kvm/introspection/kvmi_msg.c | 12 +++++++ 5 files changed, 105 insertions(+), 4 deletions(-) diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst index efde4b771586..d848e56f42e9 100644 --- a/Documentation/virt/kvm/kvmi.rst +++ b/Documentation/virt/kvm/kvmi.rst @@ -223,3 +223,38 @@ device-specific memory (DMA, emulated MMIO, reserved by a passthrough device etc.). It is up to the user to determine, using the guest operating system data structures, the areas that are safe to access (code, stack, heap etc.). + +Commands +-------- + +The following C structures are meant to be used directly when communicating +over the wire. The peer that detects any size mismatch should simply close +the connection and report the error. + +1. KVMI_GET_VERSION +------------------- + +:Architectures: all +:Versions: >= 1 +:Parameters: none +:Returns: + +:: + + struct kvmi_error_code; + struct kvmi_get_version_reply { + __u32 version; + __u32 padding; + }; + +Returns the introspection API version. + +This command is always allowed and successful (if the introspection is +built in kernel). + +The userspace should use this command to identify the commands/events +supported by the kernel side and what messages must be used for event +replies. These messages might be extended in futures versions and while +the kernel will accept shorter messages (older versions) or bigger +messages (newer versions, ignoring the extra information) it will not +accept bigger/newer event replies. diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h index 6fdaa92393a4..b0a5b72d3936 100644 --- a/include/uapi/linux/kvmi.h +++ b/include/uapi/linux/kvmi.h @@ -6,11 +6,16 @@ * KVMI structures and definitions */ +#include <linux/kernel.h> +#include <linux/types.h> + enum { KVMI_VERSION = 0x00000001 }; enum { + KVMI_GET_VERSION = 2, + KVMI_NUM_MESSAGES }; @@ -40,4 +45,9 @@ struct kvmi_error_code { __u32 padding; }; +struct kvmi_get_version_reply { + __u32 version; + __u32 padding; +}; + #endif /* _UAPI__LINUX_KVMI_H */ diff --git a/tools/testing/selftests/kvm/x86_64/kvmi_test.c b/tools/testing/selftests/kvm/x86_64/kvmi_test.c index 4c1fe67c8e35..327272e266ff 100644 --- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c +++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c @@ -177,12 +177,37 @@ static void test_cmd_invalid(void) -r, kvm_strerror(-r)); } +static void test_vm_command(int cmd_id, struct kvmi_msg_hdr *req, + size_t req_size, void *rpl, size_t rpl_size) +{ + int r; + + r = do_command(cmd_id, req, req_size, rpl, rpl_size); + TEST_ASSERT(r == 0, + "Command %d failed, error %d (%s)\n", + cmd_id, -r, kvm_strerror(-r)); +} + +static void test_cmd_get_version(void) +{ + struct kvmi_get_version_reply rpl; + struct kvmi_msg_hdr req; + + test_vm_command(KVMI_GET_VERSION, &req, sizeof(req), &rpl, sizeof(rpl)); + TEST_ASSERT(rpl.version == KVMI_VERSION, + "Unexpected KVMI version %d, expecting %d\n", + rpl.version, KVMI_VERSION); + + DEBUG("KVMI version: %u\n", rpl.version); +} + static void test_introspection(struct kvm_vm *vm) { setup_socket(); hook_introspection(vm); test_cmd_invalid(); + test_cmd_get_version(); unhook_introspection(vm); } diff --git a/virt/kvm/introspection/kvmi.c b/virt/kvm/introspection/kvmi.c index 88d29408fbf1..8cd66b1dac02 100644 --- a/virt/kvm/introspection/kvmi.c +++ b/virt/kvm/introspection/kvmi.c @@ -10,6 +10,8 @@ #define KVMI_MSG_SIZE_ALLOC (sizeof(struct kvmi_msg_hdr) + KVMI_MSG_SIZE) +static DECLARE_BITMAP(Kvmi_always_allowed_commands, KVMI_NUM_COMMANDS); + static struct kmem_cache *msg_cache; void *kvmi_msg_alloc(void) @@ -43,8 +45,16 @@ static int kvmi_cache_create(void) return 0; } +static void setup_always_allowed_commands(void) +{ + bitmap_zero(Kvmi_always_allowed_commands, KVMI_NUM_COMMANDS); + set_bit(KVMI_GET_VERSION, Kvmi_always_allowed_commands); +} + int kvmi_init(void) { + setup_always_allowed_commands(); + return kvmi_cache_create(); } @@ -71,6 +81,9 @@ alloc_kvmi(struct kvm *kvm, const struct kvm_introspection_hook *hook) BUILD_BUG_ON(sizeof(hook->uuid) != sizeof(kvmi->uuid)); memcpy(&kvmi->uuid, &hook->uuid, sizeof(kvmi->uuid)); + bitmap_copy(kvmi->cmd_allow_mask, Kvmi_always_allowed_commands, + KVMI_NUM_COMMANDS); + kvmi->kvm = kvm; return kvmi; @@ -282,8 +295,8 @@ int kvmi_ioctl_event(struct kvm *kvm, void __user *argp) return err; } -static void kvmi_control_allowed_commands(struct kvm_introspection *kvmi, - int id, bool allow) +static int kvmi_control_allowed_commands(struct kvm_introspection *kvmi, + int id, bool allow) { int all_commands = -1; @@ -294,10 +307,16 @@ static void kvmi_control_allowed_commands(struct kvm_introspection *kvmi, set_bit(id, kvmi->cmd_allow_mask); } else { if (id == all_commands) - bitmap_zero(kvmi->cmd_allow_mask, KVMI_NUM_COMMANDS); + bitmap_copy(kvmi->cmd_allow_mask, + Kvmi_always_allowed_commands, + KVMI_NUM_COMMANDS); + else if (test_bit(id, Kvmi_always_allowed_commands)) + return -EPERM; else clear_bit(id, kvmi->cmd_allow_mask); } + + return 0; } int kvmi_ioctl_command(struct kvm *kvm, void __user *argp) @@ -314,7 +333,7 @@ int kvmi_ioctl_command(struct kvm *kvm, void __user *argp) kvmi = KVMI(kvm); if (kvmi) - kvmi_control_allowed_commands(kvmi, id, allow); + err = kvmi_control_allowed_commands(kvmi, id, allow); else err = -EFAULT; diff --git a/virt/kvm/introspection/kvmi_msg.c b/virt/kvm/introspection/kvmi_msg.c index 02fc5d95fef6..9efcd896f0c6 100644 --- a/virt/kvm/introspection/kvmi_msg.c +++ b/virt/kvm/introspection/kvmi_msg.c @@ -103,11 +103,23 @@ static bool is_command_allowed(struct kvm_introspection *kvmi, u16 id) return id < KVMI_NUM_COMMANDS && test_bit(id, kvmi->cmd_allow_mask); } +static int handle_get_version(struct kvm_introspection *kvmi, + const struct kvmi_msg_hdr *msg, const void *req) +{ + struct kvmi_get_version_reply rpl; + + memset(&rpl, 0, sizeof(rpl)); + rpl.version = KVMI_VERSION; + + return kvmi_msg_vm_reply(kvmi, msg, 0, &rpl, sizeof(rpl)); +} + /* * These commands are executed by the receiving thread/worker. */ static int(*const msg_vm[])(struct kvm_introspection *, const struct kvmi_msg_hdr *, const void *) = { + [KVMI_GET_VERSION] = handle_get_version, }; static bool is_vm_command(u16 id) _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
