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dell-wmi: Stop storing pointers to DMI tables

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The dmi_walk function maps the DMI table, walks it, and unmaps it.
This means that the dell_bios_hotkey_table that find_hk_type stores
points to unmapped memory by the time it gets read.

I've been able to trigger crashes caused by the stale pointer a
couple of times, but never on a stock kernel.

Fix it by generating the keymap in the dmi_walk callback instead of
storing a pointer.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
This commit is contained in:
Andy Lutomirski 2016-02-15 08:32:33 -08:00 committed by Darren Hart
parent 0c41a08e13
commit 18b6f80f50
1 changed files with 46 additions and 28 deletions
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74
drivers/platform/x86/dell-wmi.c
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@ -120,7 +120,10 @@ struct dell_bios_hotkey_table {
};
static const struct dell_bios_hotkey_table *dell_bios_hotkey_table;
struct dell_dmi_results {
int err;
struct key_entry *keymap;
};
/* Uninitialized entries here are KEY_RESERVED == 0. */
static const u16 bios_to_linux_keycode[256] __initconst = {
@ -337,20 +340,34 @@ static void dell_wmi_notify(u32 value, void *context)
kfree(obj);
}
static const struct key_entry * __init dell_wmi_prepare_new_keymap(void)
static void __init handle_dmi_entry(const struct dmi_header *dm,
void *opaque)
{
int hotkey_num = (dell_bios_hotkey_table->header.length - 4) /
sizeof(struct dell_bios_keymap_entry);
struct dell_dmi_results *results = opaque;
struct dell_bios_hotkey_table *table;
struct key_entry *keymap;
int i;
int hotkey_num, i;
if (results->err || results->keymap)
return; /* We already found the hotkey table. */
if (dm->type != 0xb2 || dm->length <= 6)
return;
table = container_of(dm, struct dell_bios_hotkey_table, header);
hotkey_num = (table->header.length - 4) /
sizeof(struct dell_bios_keymap_entry);
keymap = kcalloc(hotkey_num + 1, sizeof(struct key_entry), GFP_KERNEL);
if (!keymap)
return NULL;
if (!keymap) {
results->err = -ENOMEM;
return;
}
for (i = 0; i < hotkey_num; i++) {
const struct dell_bios_keymap_entry *bios_entry =
&dell_bios_hotkey_table->keymap[i];
&table->keymap[i];
/* Uninitialized entries are 0 aka KEY_RESERVED. */
u16 keycode = (bios_entry->keycode <
@ -379,11 +396,12 @@ static const struct key_entry * __init dell_wmi_prepare_new_keymap(void)
keymap[hotkey_num].type = KE_END;
return keymap;
results->keymap = keymap;
}
static int __init dell_wmi_input_setup(void)
{
struct dell_dmi_results dmi_results = {};
int err;
dell_wmi_input_dev = input_allocate_device();
@ -394,20 +412,31 @@ static int __init dell_wmi_input_setup(void)
dell_wmi_input_dev->phys = "wmi/input0";
dell_wmi_input_dev->id.bustype = BUS_HOST;
if (dell_new_hk_type) {
const struct key_entry *keymap = dell_wmi_prepare_new_keymap();
if (!keymap) {
err = -ENOMEM;
goto err_free_dev;
}
if (dmi_walk(handle_dmi_entry, &dmi_results)) {
/*
* Historically, dell-wmi ignored dmi_walk errors. A failure
* is certainly surprising, but it probably just indicates
* a very old laptop.
*/
pr_warn("no DMI; using the old-style hotkey interface\n");
}
err = sparse_keymap_setup(dell_wmi_input_dev, keymap, NULL);
if (dmi_results.err) {
err = dmi_results.err;
goto err_free_dev;
}
if (dmi_results.keymap) {
dell_new_hk_type = true;
err = sparse_keymap_setup(dell_wmi_input_dev,
dmi_results.keymap, NULL);
/*
* Sparse keymap library makes a copy of keymap so we
* don't need the original one that was allocated.
*/
kfree(keymap);
kfree(dmi_results.keymap);
} else {
err = sparse_keymap_setup(dell_wmi_input_dev,
dell_wmi_legacy_keymap, NULL);
@ -434,15 +463,6 @@ static void dell_wmi_input_destroy(void)
input_unregister_device(dell_wmi_input_dev);
}
static void __init find_hk_type(const struct dmi_header *dm, void *dummy)
{
if (dm->type == 0xb2 && dm->length > 6) {
dell_new_hk_type = true;
dell_bios_hotkey_table =
container_of(dm, struct dell_bios_hotkey_table, header);
}
}
/*
* Descriptor buffer is 128 byte long and contains:
*
@ -524,8 +544,6 @@ static int __init dell_wmi_init(void)
if (err)
return err;
dmi_walk(find_hk_type, NULL);
err = dell_wmi_input_setup();
if (err)
return err;