[PATCH] tpm: tpm_crb: Fix an improper buffer size calculation bug

From: Seunghun Han <kkamagui@gmail.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Peter Huewe <peterhuewe@gmx.de>,
	linux-integrity@vger.kernel.org (open list:TPM DEVICE DRIVER),
	linux-kernel@vger.kernel.org, Seunghun Han <kkamagui@gmail.com>
Subject: [PATCH] tpm: tpm_crb: Fix an improper buffer size calculation bug
Date: Mon, 26 Aug 2019 16:44:00 +0900	[thread overview]
Message-ID: <20190826074400.54794-1-kkamagui@gmail.com> (raw)

I'm Seunghun Han and work at the Affiliated Institute of ETRI. I found
a bug related to improper buffer size calculation in crb_fixup_cmd_size
function.

When the TPM CRB regions are two or more, the crb_map_io function calls
crb_fixup_cmd_size twice to calculate command buffer size and response
buffer size. The purpose of crb_fixup_cmd_size function is to trust
the ACPI region information.

However, the function compares only io_res argument with start and size
arguments.  It means the io_res argument is one of command buffer and
response buffer regions. It also means the other region is not calculated
correctly by the function because io_res argument doesn't cover all TPM
CRB regions.

To fix this bug, I change crb_check_resource function for storing all TPB
CRB regions to a list and use the list to calculate command buffer size
and response buffer size correctly.

Signed-off-by: Seunghun Han <kkamagui@gmail.com>
---
 drivers/char/tpm/tpm_crb.c | 50 ++++++++++++++++++++++++++------------
 1 file changed, 34 insertions(+), 16 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index e59f1f91d7f3..b0e94e02e5eb 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -442,6 +442,9 @@ static int crb_check_resource(struct acpi_resource *ares, void *data)
 	    acpi_dev_resource_address_space(ares, &win)) {
 		*io_res = *res;
 		io_res->name = NULL;
+
+		/* Add this TPM CRB resource to the list */
+		return 0;
 	}
 
 	return 1;
@@ -471,20 +474,30 @@ static void __iomem *crb_map_res(struct device *dev, struct crb_priv *priv,
  * region vs the registers. Trust the ACPI region. Such broken systems
  * probably cannot send large TPM commands since the buffer will be truncated.
  */
-static u64 crb_fixup_cmd_size(struct device *dev, struct resource *io_res,
+static u64 crb_fixup_cmd_size(struct device *dev, struct list_head *resources,
 			      u64 start, u64 size)
 {
-	if (io_res->start > start || io_res->end < start)
-		return size;
+	struct resource_entry *pos;
+	struct resource *cur_res;
+
+	/* Check all TPM CRB resources with the start and size values */
+	resource_list_for_each_entry(pos, resources) {
+		cur_res = pos->res;
+
+		if (cur_res->start > start || cur_res->end < start)
+			continue;
 
-	if (start + size - 1 <= io_res->end)
-		return size;
+		if (start + size - 1 <= cur_res->end)
+			return size;
 
-	dev_err(dev,
-		FW_BUG "ACPI region does not cover the entire command/response buffer. %pr vs %llx %llx\n",
-		io_res, start, size);
+		dev_err(dev,
+			FW_BUG "ACPI region does not cover the entire command/response buffer. %pr vs %llx %llx\n",
+			cur_res, start, size);
+
+		return cur_res->end - start + 1;
+	}
 
-	return io_res->end - start + 1;
+	return size;
 }
 
 static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
@@ -506,16 +519,18 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 				     &io_res);
 	if (ret < 0)
 		return ret;
-	acpi_dev_free_resource_list(&resources);
 
 	if (resource_type(&io_res) != IORESOURCE_MEM) {
 		dev_err(dev, FW_BUG "TPM2 ACPI table does not define a memory resource\n");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out_early;
 	}
 
 	priv->iobase = devm_ioremap_resource(dev, &io_res);
-	if (IS_ERR(priv->iobase))
-		return PTR_ERR(priv->iobase);
+	if (IS_ERR(priv->iobase)) {
+		ret = PTR_ERR(priv->iobase);
+		goto out_early;
+	}
 
 	/* The ACPI IO region starts at the head area and continues to include
 	 * the control area, as one nice sane region except for some older
@@ -532,7 +547,7 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 
 	ret = __crb_request_locality(dev, priv, 0);
 	if (ret)
-		return ret;
+		goto out_early;
 
 	priv->regs_t = crb_map_res(dev, priv, &io_res, buf->control_address,
 				   sizeof(struct crb_regs_tail));
@@ -552,7 +567,7 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 	pa_high = ioread32(&priv->regs_t->ctrl_cmd_pa_high);
 	pa_low  = ioread32(&priv->regs_t->ctrl_cmd_pa_low);
 	cmd_pa = ((u64)pa_high << 32) | pa_low;
-	cmd_size = crb_fixup_cmd_size(dev, &io_res, cmd_pa,
+	cmd_size = crb_fixup_cmd_size(dev, &resources, cmd_pa,
 				      ioread32(&priv->regs_t->ctrl_cmd_size));
 
 	dev_dbg(dev, "cmd_hi = %X cmd_low = %X cmd_size %X\n",
@@ -566,7 +581,7 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 
 	memcpy_fromio(&__rsp_pa, &priv->regs_t->ctrl_rsp_pa, 8);
 	rsp_pa = le64_to_cpu(__rsp_pa);
-	rsp_size = crb_fixup_cmd_size(dev, &io_res, rsp_pa,
+	rsp_size = crb_fixup_cmd_size(dev, &resources, rsp_pa,
 				      ioread32(&priv->regs_t->ctrl_rsp_size));
 
 	if (cmd_pa != rsp_pa) {
@@ -596,6 +611,9 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 
 	__crb_relinquish_locality(dev, priv, 0);
 
+out_early:
+	acpi_dev_free_resource_list(&resources);
+
 	return ret;
 }
 
-- 
2.21.0

