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platform/x86: dell-smbios: Add filtering support
When a userspace interface is introduced to dell-smbios filtering support will be used to make sure that userspace doesn't make calls deemed unsafe or that can cause the kernel drivers to get out of sync. A blacklist is provided for the following: - Items that are in use by other kernel drivers - Items that are deemed unsafe (diagnostics, write-once, etc) - Any items in the blacklist will be rejected. Following that a whitelist is provided as follows: - Each item has an associated capability. If a userspace interface accesses this item, that capability will be tested to filter the request. - If the process provides CAP_SYS_RAWIO the whitelist will be overridden. When an item is not in the blacklist, or whitelist and the process is run with insufficient capabilities the call will be rejected. Signed-off-by: Mario Limonciello <mario.limonciello@dell.com> Reviewed-by: Edward O'Callaghan <quasisec@google.com> Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>
This commit is contained in:
Mario Limonciello
Darren Hart (VMware)
parent
da1f607ed6
commit
1f8543a5d6
@ -24,6 +24,7 @@
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#include <linux/slab.h>
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#include "dell-smbios.h"
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static u32 da_supported_commands;
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static int da_num_tokens;
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static struct platform_device *platform_device;
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static struct calling_interface_token *da_tokens;
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@ -38,6 +39,91 @@ struct smbios_device {
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int (*call_fn)(struct calling_interface_buffer *);
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};
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struct smbios_call {
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u32 need_capability;
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int cmd_class;
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int cmd_select;
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};
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/* calls that are whitelisted for given capabilities */
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static struct smbios_call call_whitelist[] = {
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/* generally tokens are allowed, but may be further filtered or
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* restricted by token blacklist or whitelist
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*/
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{CAP_SYS_ADMIN, CLASS_TOKEN_READ, SELECT_TOKEN_STD},
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{CAP_SYS_ADMIN, CLASS_TOKEN_READ, SELECT_TOKEN_AC},
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{CAP_SYS_ADMIN, CLASS_TOKEN_READ, SELECT_TOKEN_BAT},
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{CAP_SYS_ADMIN, CLASS_TOKEN_WRITE, SELECT_TOKEN_STD},
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{CAP_SYS_ADMIN, CLASS_TOKEN_WRITE, SELECT_TOKEN_AC},
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{CAP_SYS_ADMIN, CLASS_TOKEN_WRITE, SELECT_TOKEN_BAT},
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/* used by userspace: fwupdate */
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{CAP_SYS_ADMIN, CLASS_ADMIN_PROP, SELECT_ADMIN_PROP},
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/* used by userspace: fwupd */
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{CAP_SYS_ADMIN, CLASS_INFO, SELECT_DOCK},
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{CAP_SYS_ADMIN, CLASS_FLASH_INTERFACE, SELECT_FLASH_INTERFACE},
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};
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/* calls that are explicitly blacklisted */
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static struct smbios_call call_blacklist[] = {
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{0x0000, 01, 07}, /* manufacturing use */
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{0x0000, 06, 05}, /* manufacturing use */
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{0x0000, 11, 03}, /* write once */
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{0x0000, 11, 07}, /* write once */
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{0x0000, 11, 11}, /* write once */
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{0x0000, 19, -1}, /* diagnostics */
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/* handled by kernel: dell-laptop */
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{0x0000, CLASS_INFO, SELECT_RFKILL},
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{0x0000, CLASS_KBD_BACKLIGHT, SELECT_KBD_BACKLIGHT},
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};
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struct token_range {
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u32 need_capability;
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u16 min;
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u16 max;
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};
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/* tokens that are whitelisted for given capabilities */
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static struct token_range token_whitelist[] = {
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/* used by userspace: fwupdate */
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{CAP_SYS_ADMIN, CAPSULE_EN_TOKEN, CAPSULE_DIS_TOKEN},
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/* can indicate to userspace that WMI is needed */
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{0x0000, WSMT_EN_TOKEN, WSMT_DIS_TOKEN}
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};
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/* tokens that are explicitly blacklisted */
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static struct token_range token_blacklist[] = {
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{0x0000, 0x0058, 0x0059}, /* ME use */
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{0x0000, 0x00CD, 0x00D0}, /* raid shadow copy */
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{0x0000, 0x013A, 0x01FF}, /* sata shadow copy */
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{0x0000, 0x0175, 0x0176}, /* write once */
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{0x0000, 0x0195, 0x0197}, /* diagnostics */
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{0x0000, 0x01DC, 0x01DD}, /* manufacturing use */
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{0x0000, 0x027D, 0x0284}, /* diagnostics */
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{0x0000, 0x02E3, 0x02E3}, /* manufacturing use */
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{0x0000, 0x02FF, 0x02FF}, /* manufacturing use */
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{0x0000, 0x0300, 0x0302}, /* manufacturing use */
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{0x0000, 0x0325, 0x0326}, /* manufacturing use */
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{0x0000, 0x0332, 0x0335}, /* fan control */
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{0x0000, 0x0350, 0x0350}, /* manufacturing use */
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{0x0000, 0x0363, 0x0363}, /* manufacturing use */
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{0x0000, 0x0368, 0x0368}, /* manufacturing use */
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{0x0000, 0x03F6, 0x03F7}, /* manufacturing use */
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{0x0000, 0x049E, 0x049F}, /* manufacturing use */
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{0x0000, 0x04A0, 0x04A3}, /* disagnostics */
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{0x0000, 0x04E6, 0x04E7}, /* manufacturing use */
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{0x0000, 0x4000, 0x7FFF}, /* internal BIOS use */
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{0x0000, 0x9000, 0x9001}, /* internal BIOS use */
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{0x0000, 0xA000, 0xBFFF}, /* write only */
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{0x0000, 0xEFF0, 0xEFFF}, /* internal BIOS use */
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/* handled by kernel: dell-laptop */
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{0x0000, BRIGHTNESS_TOKEN, BRIGHTNESS_TOKEN},
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{0x0000, KBD_LED_OFF_TOKEN, KBD_LED_AUTO_TOKEN},
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{0x0000, KBD_LED_AC_TOKEN, KBD_LED_AC_TOKEN},
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{0x0000, KBD_LED_AUTO_25_TOKEN, KBD_LED_AUTO_75_TOKEN},
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{0x0000, KBD_LED_AUTO_100_TOKEN, KBD_LED_AUTO_100_TOKEN},
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{0x0000, GLOBAL_MIC_MUTE_ENABLE, GLOBAL_MIC_MUTE_DISABLE},
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};
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static LIST_HEAD(smbios_device_list);
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int dell_smbios_error(int value)
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@ -90,6 +176,110 @@ void dell_smbios_unregister_device(struct device *d)
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}
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EXPORT_SYMBOL_GPL(dell_smbios_unregister_device);
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int dell_smbios_call_filter(struct device *d,
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struct calling_interface_buffer *buffer)
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{
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u16 t = 0;
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int i;
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/* can't make calls over 30 */
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if (buffer->cmd_class > 30) {
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dev_dbg(d, "class too big: %u\n", buffer->cmd_class);
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return -EINVAL;
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}
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/* supported calls on the particular system */
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if (!(da_supported_commands & (1 << buffer->cmd_class))) {
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dev_dbg(d, "invalid command, supported commands: 0x%8x\n",
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da_supported_commands);
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return -EINVAL;
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}
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/* match against call blacklist */
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for (i = 0; i < ARRAY_SIZE(call_blacklist); i++) {
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if (buffer->cmd_class != call_blacklist[i].cmd_class)
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continue;
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if (buffer->cmd_select != call_blacklist[i].cmd_select &&
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call_blacklist[i].cmd_select != -1)
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continue;
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dev_dbg(d, "blacklisted command: %u/%u\n",
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buffer->cmd_class, buffer->cmd_select);
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return -EINVAL;
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}
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/* if a token call, find token ID */
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if ((buffer->cmd_class == CLASS_TOKEN_READ ||
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buffer->cmd_class == CLASS_TOKEN_WRITE) &&
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buffer->cmd_select < 3) {
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/* find the matching token ID */
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for (i = 0; i < da_num_tokens; i++) {
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if (da_tokens[i].location != buffer->input[0])
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continue;
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t = da_tokens[i].tokenID;
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break;
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}
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/* token call; but token didn't exist */
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if (!t) {
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dev_dbg(d, "token at location %04x doesn't exist\n",
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buffer->input[0]);
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return -EINVAL;
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}
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/* match against token blacklist */
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for (i = 0; i < ARRAY_SIZE(token_blacklist); i++) {
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if (!token_blacklist[i].min || !token_blacklist[i].max)
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continue;
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if (t >= token_blacklist[i].min &&
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t <= token_blacklist[i].max)
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return -EINVAL;
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}
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/* match against token whitelist */
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for (i = 0; i < ARRAY_SIZE(token_whitelist); i++) {
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if (!token_whitelist[i].min || !token_whitelist[i].max)
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continue;
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if (t < token_whitelist[i].min ||
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t > token_whitelist[i].max)
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continue;
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if (!token_whitelist[i].need_capability ||
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capable(token_whitelist[i].need_capability)) {
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dev_dbg(d, "whitelisted token: %x\n", t);
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return 0;
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}
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}
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}
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/* match against call whitelist */
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for (i = 0; i < ARRAY_SIZE(call_whitelist); i++) {
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if (buffer->cmd_class != call_whitelist[i].cmd_class)
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continue;
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if (buffer->cmd_select != call_whitelist[i].cmd_select)
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continue;
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if (!call_whitelist[i].need_capability ||
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capable(call_whitelist[i].need_capability)) {
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dev_dbg(d, "whitelisted capable command: %u/%u\n",
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buffer->cmd_class, buffer->cmd_select);
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return 0;
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}
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dev_dbg(d, "missing capability %d for %u/%u\n",
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call_whitelist[i].need_capability,
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buffer->cmd_class, buffer->cmd_select);
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}
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/* not in a whitelist, only allow processes with capabilities */
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if (capable(CAP_SYS_RAWIO)) {
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dev_dbg(d, "Allowing %u/%u due to CAP_SYS_RAWIO\n",
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buffer->cmd_class, buffer->cmd_select);
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return 0;
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}
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return -EACCES;
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}
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EXPORT_SYMBOL_GPL(dell_smbios_call_filter);
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int dell_smbios_call(struct calling_interface_buffer *buffer)
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{
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int (*call_fn)(struct calling_interface_buffer *) = NULL;
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@ -168,6 +358,8 @@ static void __init parse_da_table(const struct dmi_header *dm)
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if (dm->length < 17)
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return;
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da_supported_commands = table->supportedCmds;
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new_da_tokens = krealloc(da_tokens, (da_num_tokens + tokens) *
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sizeof(struct calling_interface_token),
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GFP_KERNEL);
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@ -26,9 +26,14 @@
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#define SELECT_TOKEN_AC 2
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#define CLASS_KBD_BACKLIGHT 4
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#define SELECT_KBD_BACKLIGHT 11
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#define CLASS_FLASH_INTERFACE 7
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#define SELECT_FLASH_INTERFACE 3
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#define CLASS_ADMIN_PROP 10
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#define SELECT_ADMIN_PROP 3
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#define CLASS_INFO 17
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#define SELECT_RFKILL 11
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#define SELECT_APP_REGISTRATION 3
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#define SELECT_DOCK 22
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/* Tokens used in kernel drivers, any of these
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* should be filtered from userspace access
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@ -44,6 +49,10 @@
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#define KBD_LED_AUTO_100_TOKEN 0x02F6
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#define GLOBAL_MIC_MUTE_ENABLE 0x0364
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#define GLOBAL_MIC_MUTE_DISABLE 0x0365
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/* tokens whitelisted to userspace use */
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#define CAPSULE_EN_TOKEN 0x0461
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#define CAPSULE_DIS_TOKEN 0x0462
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#define WSMT_EN_TOKEN 0x04EC
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#define WSMT_DIS_TOKEN 0x04ED
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@ -80,6 +89,8 @@ int dell_smbios_register_device(struct device *d, void *call_fn);
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void dell_smbios_unregister_device(struct device *d);
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int dell_smbios_error(int value);
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int dell_smbios_call_filter(struct device *d,
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struct calling_interface_buffer *buffer);
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int dell_smbios_call(struct calling_interface_buffer *buffer);
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struct calling_interface_token *dell_smbios_find_token(int tokenid);
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