x86/boot: Fix memremap of setup_indirect structures

As documented, the setup_indirect structure is nested inside
the setup_data structures in the setup_data list. The code currently
accesses the fields inside the setup_indirect structure but only
the sizeof(struct setup_data) is being memremapped. No crash
occurred but this is just due to how the area is remapped under the
covers.

Properly memremap both the setup_data and setup_indirect structures
in these cases before accessing them.

Fixes: b3c72fc9a78e ("x86/boot: Introduce setup_indirect")
Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1645668456-22036-2-git-send-email-ross.philipson@oracle.com

1 files changed, 61 insertions, 16 deletions

diff --git a/arch/x86/kernel/ksysfs.c b/arch/x86/kernel/ksysfs.c
index d0a19121c6a4..257892fcefa7 100644
--- a/arch/x86/kernel/ksysfs.c
+++ b/arch/x86/kernel/ksysfs.c
@@ -91,26 +91,41 @@ static int get_setup_data_paddr(int nr, u64 *paddr)
 
 static int __init get_setup_data_size(int nr, size_t *size)
 {
-	int i = 0;
+	u64 pa_data = boot_params.hdr.setup_data, pa_next;
+	struct setup_indirect *indirect;
 	struct setup_data *data;
-	u64 pa_data = boot_params.hdr.setup_data;
+	int i = 0;
+	u32 len;
 
 	while (pa_data) {
 		data = memremap(pa_data, sizeof(*data), MEMREMAP_WB);
 		if (!data)
 			return -ENOMEM;
+		pa_next = data->next;
+
 		if (nr == i) {
-			if (data->type == SETUP_INDIRECT &&
-			    ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT)
-				*size = ((struct setup_indirect *)data->data)->len;
-			else
+			if (data->type == SETUP_INDIRECT) {
+				len = sizeof(*data) + data->len;
+				memunmap(data);
+				data = memremap(pa_data, len, MEMREMAP_WB);
+				if (!data)
+					return -ENOMEM;
+
+				indirect = (struct setup_indirect *)data->data;
+
+				if (indirect->type != SETUP_INDIRECT)
+					*size = indirect->len;
+				else
+					*size = data->len;
+			} else {
 				*size = data->len;
+			}
 
 			memunmap(data);
 			return 0;
 		}
 
-		pa_data = data->next;
+		pa_data = pa_next;
 		memunmap(data);
 		i++;
 	}
@@ -120,9 +135,11 @@ static int __init get_setup_data_size(int nr, size_t *size)
 static ssize_t type_show(struct kobject *kobj,
 			 struct kobj_attribute *attr, char *buf)
 {
+	struct setup_indirect *indirect;
+	struct setup_data *data;
 	int nr, ret;
 	u64 paddr;
-	struct setup_data *data;
+	u32 len;
 
 	ret = kobj_to_setup_data_nr(kobj, &nr);
 	if (ret)
@@ -135,10 +152,20 @@ static ssize_t type_show(struct kobject *kobj,
 	if (!data)
 		return -ENOMEM;
 
-	if (data->type == SETUP_INDIRECT)
-		ret = sprintf(buf, "0x%x\n", ((struct setup_indirect *)data->data)->type);
-	else
+	if (data->type == SETUP_INDIRECT) {
+		len = sizeof(*data) + data->len;
+		memunmap(data);
+		data = memremap(paddr, len, MEMREMAP_WB);
+		if (!data)
+			return -ENOMEM;
+
+		indirect = (struct setup_indirect *)data->data;
+
+		ret = sprintf(buf, "0x%x\n", indirect->type);
+	} else {
 		ret = sprintf(buf, "0x%x\n", data->type);
+	}
+
 	memunmap(data);
 	return ret;
 }
@@ -149,9 +176,10 @@ static ssize_t setup_data_data_read(struct file *fp,
 				    char *buf,
 				    loff_t off, size_t count)
 {
+	struct setup_indirect *indirect;
+	struct setup_data *data;
 	int nr, ret = 0;
 	u64 paddr, len;
-	struct setup_data *data;
 	void *p;
 
 	ret = kobj_to_setup_data_nr(kobj, &nr);
@@ -165,10 +193,27 @@ static ssize_t setup_data_data_read(struct file *fp,
 	if (!data)
 		return -ENOMEM;
 
-	if (data->type == SETUP_INDIRECT &&
-	    ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT) {
-		paddr = ((struct setup_indirect *)data->data)->addr;
-		len = ((struct setup_indirect *)data->data)->len;
+	if (data->type == SETUP_INDIRECT) {
+		len = sizeof(*data) + data->len;
+		memunmap(data);
+		data = memremap(paddr, len, MEMREMAP_WB);
+		if (!data)
+			return -ENOMEM;
+
+		indirect = (struct setup_indirect *)data->data;
+
+		if (indirect->type != SETUP_INDIRECT) {
+			paddr = indirect->addr;
+			len = indirect->len;
+		} else {
+			/*
+			 * Even though this is technically undefined, return
+			 * the data as though it is a normal setup_data struct.
+			 * This will at least allow it to be inspected.
+			 */
+			paddr += sizeof(*data);
+			len = data->len;
+		}
 	} else {
 		paddr += sizeof(*data);
 		len = data->len;