firmware: dmi_scan: Trim DMI table length before exporting it

The SMBIOS v3 entry points specify a maximum length for the DMI table,
not the exact length. Thus there may be garbage after the end-of-table
marker, which we don't want to export to user-space. Adjust dmi_len
when we find the end-of-table marker, so that only the actual table
payload is exported.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Ivan Khoronzhuk <ivan.khoronzhuk@globallogic.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 14a89123cb7c..7fdf2868a276 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -108,6 +108,9 @@ static void dmi_decode_table(u8 *buf,
                 if (data - buf < dmi_len - 1)
                         decode(dm, private_data);
 
+                data += 2;
+                i++;
+
                 /*
                  * 7.45 End-of-Table (Type 127) [SMBIOS reference spec v3.0.0]
                  * For tables behind a 64-bit entry point, we have no item
@@ -118,10 +121,11 @@ static void dmi_decode_table(u8 *buf,
                  */
                 if (!dmi_num && dm->type == DMI_ENTRY_END_OF_TABLE)
                         break;
-
-                data += 2;
-                i++;
         }
+
+        /* Trim DMI table length if needed */
+        if (dmi_len > data - buf)
+                dmi_len = data - buf;
 }
 
 static phys_addr_t dmi_base;
@@ -130,8 +134,9 @@ static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
                 void *))
 {
         u8 *buf;
+        u32 orig_dmi_len = dmi_len;
 
-        buf = dmi_early_remap(dmi_base, dmi_len);
+        buf = dmi_early_remap(dmi_base, orig_dmi_len);
         if (buf == NULL)
                 return -1;
 
@@ -139,7 +144,7 @@ static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
 
         add_device_randomness(buf, dmi_len);
 
-        dmi_early_unmap(buf, dmi_len);
+        dmi_early_unmap(buf, orig_dmi_len);
         return 0;
 }