6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dan Williams dan.j.williams@intel.com
[ Upstream commit db10cb9b574675402bfd8fe1a31aafdd45b002df ]
CONFIG_DEBUG_SG highlights that get_{report,ext_report,derived_key)()} are passing stack buffers as the @req_buf argument to handle_guest_request(), generating a Call Trace of the following form:
WARNING: CPU: 0 PID: 1175 at include/linux/scatterlist.h:187 enc_dec_message+0x518/0x5b0 [sev_guest] [..] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023 RIP: 0010:enc_dec_message+0x518/0x5b0 [sev_guest] Call Trace: <TASK> [..] handle_guest_request+0x135/0x520 [sev_guest] get_ext_report+0x1ec/0x3e0 [sev_guest] snp_guest_ioctl+0x157/0x200 [sev_guest]
Note that the above Call Trace was with the DEBUG_SG BUG_ON()s converted to WARN_ON()s.
This is benign as long as there are no hardware crypto accelerators loaded for the aead cipher, and no subsequent dma_map_sg() is performed on the scatterlist. However, sev-guest can not assume the presence of an aead accelerator nor can it assume that CONFIG_DEBUG_SG is disabled.
Resolve this bug by allocating virt_addr_valid() memory, similar to the other buffers am @snp_dev instance carries, to marshal requests from user buffers to kernel buffers.
Reported-by: Peter Gonda pgonda@google.com Closes: http://lore.kernel.org/r/CAMkAt6r2VPPMZ__SQfJse8qWsUyYW3AgYbOUVM0S_Vtk=KvkxQ... Fixes: fce96cf04430 ("virt: Add SEV-SNP guest driver") Cc: Borislav Petkov bp@alien8.de Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Dionna Glaze dionnaglaze@google.com Cc: Jeremi Piotrowski jpiotrowski@linux.microsoft.com Tested-by: Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com Reviewed-by: Tom Lendacky thomas.lendacky@amd.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/virt/coco/sev-guest/sev-guest.c | 45 ++++++++++++++----------- 1 file changed, 25 insertions(+), 20 deletions(-)
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c index 5cdc972e5ef4a..c47e54b2a865e 100644 --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -57,6 +57,11 @@ struct snp_guest_dev {
struct snp_secrets_page_layout *layout; struct snp_req_data input; + union { + struct snp_report_req report; + struct snp_derived_key_req derived_key; + struct snp_ext_report_req ext_report; + } req; u32 *os_area_msg_seqno; u8 *vmpck; }; @@ -475,8 +480,8 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg) { struct snp_guest_crypto *crypto = snp_dev->crypto; + struct snp_report_req *req = &snp_dev->req.report; struct snp_report_resp *resp; - struct snp_report_req req; int rc, resp_len;
lockdep_assert_held(&snp_cmd_mutex); @@ -484,7 +489,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io if (!arg->req_data || !arg->resp_data) return -EINVAL;
- if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req))) + if (copy_from_user(req, (void __user *)arg->req_data, sizeof(*req))) return -EFAULT;
/* @@ -498,7 +503,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io return -ENOMEM;
rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg, - SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data, + SNP_MSG_REPORT_REQ, req, sizeof(*req), resp->data, resp_len); if (rc) goto e_free; @@ -513,9 +518,9 @@ 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_req *req = &snp_dev->req.derived_key; struct snp_guest_crypto *crypto = snp_dev->crypto; struct snp_derived_key_resp resp = {0}; - struct snp_derived_key_req req; int rc, resp_len; /* Response data is 64 bytes and max authsize for GCM is 16 bytes. */ u8 buf[64 + 16]; @@ -534,11 +539,11 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque if (sizeof(buf) < resp_len) return -ENOMEM;
- if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req))) + if (copy_from_user(req, (void __user *)arg->req_data, sizeof(*req))) return -EFAULT;
rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg, - SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len); + SNP_MSG_KEY_REQ, req, sizeof(*req), buf, resp_len); if (rc) return rc;
@@ -554,8 +559,8 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg) { + struct snp_ext_report_req *req = &snp_dev->req.ext_report; struct snp_guest_crypto *crypto = snp_dev->crypto; - struct snp_ext_report_req req; struct snp_report_resp *resp; int ret, npages = 0, resp_len;
@@ -564,18 +569,18 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques if (!arg->req_data || !arg->resp_data) return -EINVAL;
- if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req))) + if (copy_from_user(req, (void __user *)arg->req_data, sizeof(*req))) return -EFAULT;
/* userspace does not want certificate data */ - if (!req.certs_len || !req.certs_address) + if (!req->certs_len || !req->certs_address) goto cmd;
- if (req.certs_len > SEV_FW_BLOB_MAX_SIZE || - !IS_ALIGNED(req.certs_len, PAGE_SIZE)) + if (req->certs_len > SEV_FW_BLOB_MAX_SIZE || + !IS_ALIGNED(req->certs_len, PAGE_SIZE)) return -EINVAL;
- if (!access_ok((const void __user *)req.certs_address, req.certs_len)) + if (!access_ok((const void __user *)req->certs_address, req->certs_len)) return -EFAULT;
/* @@ -584,8 +589,8 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques * the host. If host does not supply any certs in it, then copy * zeros to indicate that certificate data was not provided. */ - memset(snp_dev->certs_data, 0, req.certs_len); - npages = req.certs_len >> PAGE_SHIFT; + memset(snp_dev->certs_data, 0, req->certs_len); + npages = req->certs_len >> PAGE_SHIFT; cmd: /* * The intermediate response buffer is used while decrypting the @@ -599,14 +604,14 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
snp_dev->input.data_npages = npages; ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg, - SNP_MSG_REPORT_REQ, &req.data, - sizeof(req.data), resp->data, resp_len); + SNP_MSG_REPORT_REQ, &req->data, + sizeof(req->data), resp->data, resp_len);
/* If certs length is invalid then copy the returned length */ if (arg->vmm_error == SNP_GUEST_VMM_ERR_INVALID_LEN) { - req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT; + req->certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
- if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req))) + if (copy_to_user((void __user *)arg->req_data, req, sizeof(*req))) ret = -EFAULT; }
@@ -614,8 +619,8 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques goto e_free;
if (npages && - copy_to_user((void __user *)req.certs_address, snp_dev->certs_data, - req.certs_len)) { + copy_to_user((void __user *)req->certs_address, snp_dev->certs_data, + req->certs_len)) { ret = -EFAULT; goto e_free; }