The patch below does not apply to the 6.16-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.16.y git checkout FETCH_HEAD git cherry-pick -x c08ba63078dd6046c279df37795cb77e784e1ec9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025081839-unmoral-mulch-990f@gregkh' --subject-prefix 'PATCH 6.16.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From c08ba63078dd6046c279df37795cb77e784e1ec9 Mon Sep 17 00:00:00 2001 From: Tom Lendacky thomas.lendacky@amd.com Date: Wed, 16 Jul 2025 15:41:35 -0500 Subject: [PATCH] virt: sev-guest: Satisfy linear mapping requirement in get_derived_key()
Commit
7ffeb2fc2670 ("x86/sev: Document requirement for linear mapping of guest request buffers")
added a check that requires the guest request buffers to be in the linear mapping. The get_derived_key() function was passing a buffer that was allocated on the stack, resulting in the call to snp_send_guest_request() returning an error.
Update the get_derived_key() function to use an allocated buffer instead of a stack buffer.
Fixes: 7ffeb2fc2670 ("x86/sev: Document requirement for linear mapping of guest request buffers") Signed-off-by: Tom Lendacky thomas.lendacky@amd.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Cc: stable@kernel.org Link: https://lore.kernel.org/9b764ca9fc79199a091aac684c4926e2080ca7a8.1752698495....
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c index d2b3ae7113ab..b01ec99106cd 100644 --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -116,13 +116,11 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg) { + struct snp_derived_key_resp *derived_key_resp __free(kfree) = NULL; struct snp_derived_key_req *derived_key_req __free(kfree) = NULL; - struct snp_derived_key_resp derived_key_resp = {0}; struct snp_msg_desc *mdesc = snp_dev->msg_desc; struct snp_guest_req req = {}; int rc, resp_len; - /* Response data is 64 bytes and max authsize for GCM is 16 bytes. */ - u8 buf[64 + 16];
if (!arg->req_data || !arg->resp_data) return -EINVAL; @@ -132,8 +130,9 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque * response payload. Make sure that it has enough space to cover the * authtag. */ - resp_len = sizeof(derived_key_resp.data) + mdesc->ctx->authsize; - if (sizeof(buf) < resp_len) + resp_len = sizeof(derived_key_resp->data) + mdesc->ctx->authsize; + derived_key_resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT); + if (!derived_key_resp) return -ENOMEM;
derived_key_req = kzalloc(sizeof(*derived_key_req), GFP_KERNEL_ACCOUNT); @@ -149,23 +148,21 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque req.vmpck_id = mdesc->vmpck_id; req.req_buf = derived_key_req; req.req_sz = sizeof(*derived_key_req); - req.resp_buf = buf; + req.resp_buf = derived_key_resp; req.resp_sz = resp_len; req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;
rc = snp_send_guest_request(mdesc, &req); arg->exitinfo2 = req.exitinfo2; - if (rc) - return rc; - - memcpy(derived_key_resp.data, buf, sizeof(derived_key_resp.data)); - if (copy_to_user((void __user *)arg->resp_data, &derived_key_resp, - sizeof(derived_key_resp))) - rc = -EFAULT; + if (!rc) { + if (copy_to_user((void __user *)arg->resp_data, derived_key_resp, + sizeof(derived_key_resp->data))) + rc = -EFAULT; + }
/* The response buffer contains the sensitive data, explicitly clear it. */ - memzero_explicit(buf, sizeof(buf)); - memzero_explicit(&derived_key_resp, sizeof(derived_key_resp)); + memzero_explicit(derived_key_resp, sizeof(*derived_key_resp)); + return rc; }