From e5e511f5d9e05e075d114318e707e191ada6e145 Mon Sep 17 00:00:00 2001 From: Muralidhara M K Date: Mon, 29 Jun 2026 21:26:34 +0530 Subject: [PATCH] platform/x86/amd/hsmp: Gate the data plane on a fully initialized socket MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit hsmp_parse_acpi_table() published sock->dev before hsmp_read_acpi_crs() had mapped virt_base_addr. sock->dev is the readiness gate for the lock-free data plane, so on a multi-socket system - where socket 0 exposes /dev/hsmp before later sockets finish probing - an ioctl aimed at a socket still in bring-up could pass the gate and dereference a NULL virt_base_addr. Publish sock->dev last with smp_store_release() once virt_base_addr, the mailbox offsets and the semaphore are initialized, and read it with smp_load_acquire() in hsmp_send_message() so a non-NULL dev guarantees the rest of the socket state is visible. Signed-off-by: Muralidhara M K Link: https://patch.msgid.link/20260629155634.1807598-5-muralidhara.mk@amd.com Reviewed-by: Ilpo Järvinen Signed-off-by: Ilpo Järvinen --- drivers/platform/x86/amd/hsmp/acpi.c | 18 ++++++++++++++++-- drivers/platform/x86/amd/hsmp/hsmp.c | 13 +++++++++++++ 2 files changed, 29 insertions(+), 2 deletions(-) diff --git a/drivers/platform/x86/amd/hsmp/acpi.c b/drivers/platform/x86/amd/hsmp/acpi.c index 1fb09251d826..72f68cef1297 100644 --- a/drivers/platform/x86/amd/hsmp/acpi.c +++ b/drivers/platform/x86/amd/hsmp/acpi.c @@ -224,7 +224,6 @@ static int hsmp_parse_acpi_table(struct device *dev, u16 sock_ind) int ret; sock->sock_ind = sock_ind; - sock->dev = dev; sock->amd_hsmp_rdwr = amd_hsmp_acpi_rdwr; sema_init(&sock->hsmp_sem, 1); @@ -237,7 +236,22 @@ static int hsmp_parse_acpi_table(struct device *dev, u16 sock_ind) return ret; /* Read mailbox offsets from DSD table */ - return hsmp_read_acpi_dsd(dev, sock); + ret = hsmp_read_acpi_dsd(dev, sock); + if (ret) + return ret; + + /* + * Publish sock->dev last. hsmp_send_message() uses it (via + * smp_load_acquire()) as the readiness gate for the lock-free data + * plane, so it must become visible only after virt_base_addr, the + * mailbox offsets and the semaphore are fully initialized. On a + * multi-socket system socket 0 exposes /dev/hsmp before later sockets + * finish probing, so without this an ioctl aimed at a socket still in + * bring-up could pass the gate and dereference a NULL virt_base_addr. + */ + smp_store_release(&sock->dev, dev); + + return 0; } static ssize_t hsmp_metric_tbl_acpi_read(struct file *filp, struct kobject *kobj, diff --git a/drivers/platform/x86/amd/hsmp/hsmp.c b/drivers/platform/x86/amd/hsmp/hsmp.c index 6a26937fc2b5..1a87931136fd 100644 --- a/drivers/platform/x86/amd/hsmp/hsmp.c +++ b/drivers/platform/x86/amd/hsmp/hsmp.c @@ -223,6 +223,19 @@ int hsmp_send_message(struct hsmp_message *msg) sock_ind = array_index_nospec(msg->sock_ind, hsmp_pdev.num_sockets); sock = &hsmp_pdev.sock[sock_ind]; + /* + * A slot exists for every possible socket, but it is only usable once + * that socket has actually been probed. Reject messages aimed at a + * socket that was never brought up or is still in bring-up, so we never + * operate on a zero-initialized semaphore or an unmapped mailbox. A + * non-NULL dev also guarantees virt_base_addr, the mailbox offsets and + * the semaphore are visible. + * + * Pairs with smp_store_release(&sock->dev) in hsmp_parse_acpi_table(). + */ + if (!smp_load_acquire(&sock->dev)) + return -ENODEV; + ret = down_interruptible(&sock->hsmp_sem); if (ret < 0) return ret;