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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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