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Subject[PATCH 38/50] firmware: Fix unaligned memory accesses in dmi-sysfs
Date
From: Mike Waychison <mikew@google.com>

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>
---
drivers/firmware/dmi-sysfs.c | 28 +++++++++++++---------------
1 files changed, 13 insertions(+), 15 deletions(-)
diff --git a/drivers/firmware/dmi-sysfs.c b/drivers/firmware/dmi-sysfs.c
index a5afd80..eb26d62 100644
--- 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++;

--
1.7.4.1


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