firmware: Fix unaligned memory accesses in dmi-sysfs

DMI entries are arranged in memory back to back with no alignment
guarantees. This means that the struct dmi_header passed to callbacks
from dmi_walk() itself isn't byte aligned.  This causes problems on
architectures that expect aligned data, such as IA64.

The dmi-sysfs patchset introduced structure member accesses through this
passed in dmi_header.  Fix this by memcpy()ing the structures to
temporary locations on stack when inspecting/copying them.

Signed-off-by: Mike Waychison <mikew@google.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/firmware/dmi-sysfs.c b/drivers/firmware/dmi-sysfs.c
index a5afd80..eb26d62 100644 (file)
--- a/drivers/firmware/dmi-sysfs.c
+++ b/drivers/firmware/dmi-sysfs.c
@@ -263,20 +263,16 @@ struct dmi_system_event_log {
        u8      supported_log_type_descriptos[0];
 } __packed;
 
-static const struct dmi_system_event_log *to_sel(const struct dmi_header *dh)
-{
-       return (const struct dmi_system_event_log *)dh;
-}
-
 #define DMI_SYSFS_SEL_FIELD(_field) \
 static ssize_t dmi_sysfs_sel_##_field(struct dmi_sysfs_entry *entry, \
                                      const struct dmi_header *dh, \
                                      char *buf) \
 { \
-       const struct dmi_system_event_log *sel = to_sel(dh); \
-       if (sizeof(*sel) > dmi_entry_length(dh)) \
+       struct dmi_system_event_log sel; \
+       if (sizeof(sel) > dmi_entry_length(dh)) \
                return -EIO; \
-       return sprintf(buf, "%u\n", sel->_field); \
+       memcpy(&sel, dh, sizeof(sel)); \
+       return sprintf(buf, "%u\n", sel._field); \
 } \
 static DMI_SYSFS_MAPPED_ATTR(sel, _field)
 
@@ -403,26 +399,28 @@ static ssize_t dmi_sel_raw_read_helper(struct dmi_sysfs_entry *entry,
                                       void *_state)
 {
        struct dmi_read_state *state = _state;
-       const struct dmi_system_event_log *sel = to_sel(dh);
+       struct dmi_system_event_log sel;
 
-       if (sizeof(*sel) > dmi_entry_length(dh))
+       if (sizeof(sel) > dmi_entry_length(dh))
                return -EIO;
 
-       switch (sel->access_method) {
+       memcpy(&sel, dh, sizeof(sel));
+
+       switch (sel.access_method) {
        case DMI_SEL_ACCESS_METHOD_IO8:
        case DMI_SEL_ACCESS_METHOD_IO2x8:
        case DMI_SEL_ACCESS_METHOD_IO16:
-               return dmi_sel_raw_read_io(entry, sel, state->buf,
+               return dmi_sel_raw_read_io(entry, &sel, state->buf,
                                           state->pos, state->count);
        case DMI_SEL_ACCESS_METHOD_PHYS32:
-               return dmi_sel_raw_read_phys32(entry, sel, state->buf,
+               return dmi_sel_raw_read_phys32(entry, &sel, state->buf,
                                               state->pos, state->count);
        case DMI_SEL_ACCESS_METHOD_GPNV:
                pr_info("dmi-sysfs: GPNV support missing.\n");
                return -EIO;
        default:
                pr_info("dmi-sysfs: Unknown access method %02x\n",
-                       sel->access_method);
+                       sel.access_method);
                return -EIO;
        }
 }
@@ -595,7 +593,7 @@ static void __init dmi_sysfs_register_handle(const struct dmi_header *dh,
        }
 
        /* Set the key */
-       entry->dh = *dh;
+       memcpy(&entry->dh, dh, sizeof(*dh));
        entry->instance = instance_counts[dh->type]++;
        entry->position = position_count++;