From c3fd16c3b98ed726294feab2f94f876290bf7b61 Mon Sep 17 00:00:00 2001 From: Zubin Mithra Date: Wed, 18 Mar 2026 13:40:13 +0000 Subject: [PATCH] virt: tdx-guest: Fix handling of host controlled 'quote' buffer length Validate host controlled value `quote_buf->out_len` that determines how many bytes of the quote are copied out to guest userspace. In TDX environments with remote attestation, quotes are not considered private, and can be forwarded to an attestation server. Catch scenarios where the host specifies a response length larger than the guest's allocation, or otherwise races modifying the response while the guest consumes it. This prevents contents beyond the pages allocated for `quote_buf` (up to TSM_REPORT_OUTBLOB_MAX) from being read out to guest userspace, and possibly forwarded in attestation requests. Recall that some deployments want per-container configs-tsm-report interfaces, so the leak may cross container protection boundaries, not just local root. Fixes: f4738f56d1dc ("virt: tdx-guest: Add Quote generation support using TSM_REPORTS") Cc: stable@vger.kernel.org Signed-off-by: Zubin Mithra Reviewed-by: Dan Williams Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: Kuppuswamy Sathyanarayanan Signed-off-by: Dan Williams --- drivers/virt/coco/tdx-guest/tdx-guest.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c index 4252b147593a..7cee97559ba2 100644 --- a/drivers/virt/coco/tdx-guest/tdx-guest.c +++ b/drivers/virt/coco/tdx-guest/tdx-guest.c @@ -171,6 +171,8 @@ static void tdx_mr_deinit(const struct attribute_group *mr_grp) #define GET_QUOTE_SUCCESS 0 #define GET_QUOTE_IN_FLIGHT 0xffffffffffffffff +#define TDX_QUOTE_MAX_LEN (GET_QUOTE_BUF_SIZE - sizeof(struct tdx_quote_buf)) + /* struct tdx_quote_buf: Format of Quote request buffer. * @version: Quote format version, filled by TD. * @status: Status code of Quote request, filled by VMM. @@ -269,6 +271,7 @@ static int tdx_report_new_locked(struct tsm_report *report, void *data) u8 *buf; struct tdx_quote_buf *quote_buf = quote_data; struct tsm_report_desc *desc = &report->desc; + u32 out_len; int ret; u64 err; @@ -306,12 +309,17 @@ static int tdx_report_new_locked(struct tsm_report *report, void *data) return ret; } - buf = kvmemdup(quote_buf->data, quote_buf->out_len, GFP_KERNEL); + out_len = READ_ONCE(quote_buf->out_len); + + if (out_len > TDX_QUOTE_MAX_LEN) + return -EFBIG; + + buf = kvmemdup(quote_buf->data, out_len, GFP_KERNEL); if (!buf) return -ENOMEM; report->outblob = buf; - report->outblob_len = quote_buf->out_len; + report->outblob_len = out_len; /* * TODO: parse the PEM-formatted cert chain out of the quote buffer when