On Fri, Aug 7, 2020 at 3:00 PM Jean Delvare <jdelvare@xxxxxxx> wrote:
>
> Special handling of the Sony VAIO EEPROMs is the last feature of the
> legacy eeprom driver that the at24 driver does not support. Adding
> this would let us deprecate and eventually remove the legacy eeprom
> driver.
>
> So add the option to specify a post-processing callback function that
> is called after reading data from the EEPROM, before it is returned
> to the user. The 24c02-vaio type is the first use case of that option:
> the callback function will mask the sensitive data for non-root users
> exactly as the legacy eeprom driver was doing.
>
> Signed-off-by: Jean Delvare <jdelvare@xxxxxxx>
> Cc: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> Bartosz, this is a different approach to solving the problem compared
> to your suggestion. It's even more generic in a way. Let me know what
> you think.
>
Yes and I like it much more than my own suggestion!
> drivers/misc/eeprom/at24.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 42 insertions(+)
>
> --- linux-5.7.orig/drivers/misc/eeprom/at24.c 2020-06-01 01:49:15.000000000 +0200
> +++ linux-5.7/drivers/misc/eeprom/at24.c 2020-08-07 12:46:47.075238130 +0200
> @@ -8,6 +8,7 @@
>
> #include <linux/acpi.h>
> #include <linux/bitops.h>
> +#include <linux/capability.h>
> #include <linux/delay.h>
> #include <linux/i2c.h>
> #include <linux/init.h>
> @@ -89,6 +90,7 @@ struct at24_data {
>
> struct nvmem_device *nvmem;
> struct regulator *vcc_reg;
> + void (*read_post)(unsigned int off, char *buf, size_t count);
>
> /*
> * Some chips tie up multiple I2C addresses; dummy devices reserve
> @@ -121,6 +123,7 @@ MODULE_PARM_DESC(at24_write_timeout, "Ti
> struct at24_chip_data {
> u32 byte_len;
> u8 flags;
> + void (*read_post)(unsigned int off, char *buf, size_t count);
> };
>
> #define AT24_CHIP_DATA(_name, _len, _flags) \
> @@ -128,6 +131,33 @@ struct at24_chip_data {
> .byte_len = _len, .flags = _flags, \
> }
>
> +#define AT24_CHIP_DATA_CB(_name, _len, _flags, _read_post) \
> + static const struct at24_chip_data _name = { \
> + .byte_len = _len, .flags = _flags, \
> + .read_post = _read_post, \
> + }
> +
> +
> +static void at24_read_post_vaio(unsigned int off, char *buf, size_t count)
> +{
> + int i;
> +
> + if (capable(CAP_SYS_ADMIN))
> + return;
> +
> + /*
> + * Hide VAIO private settings to regular users:
> + * - BIOS passwords: bytes 0x00 to 0x0f
> + * - UUID: bytes 0x10 to 0x1f
> + * - Serial number: 0xc0 to 0xdf
> + */
> + for (i = 0; i < count; i++) {
> + if ((off + i <= 0x1f) ||
> + (off + i >= 0xc0 && off + i <= 0xdf))
> + buf[i] = 0;
> + }
> +}
> +
> /* needs 8 addresses as A0-A2 are ignored */
> AT24_CHIP_DATA(at24_data_24c00, 128 / 8, AT24_FLAG_TAKE8ADDR);
> /* old variants can't be handled with this generic entry! */
> @@ -144,6 +174,10 @@ AT24_CHIP_DATA(at24_data_24mac602, 64 /
> /* spd is a 24c02 in memory DIMMs */
> AT24_CHIP_DATA(at24_data_spd, 2048 / 8,
> AT24_FLAG_READONLY | AT24_FLAG_IRUGO);
> +/* 24c02_vaio is a 24c02 on some Sony laptops */
> +AT24_CHIP_DATA_CB(at24_data_24c02_vaio, 2048 / 8,
> + AT24_FLAG_READONLY | AT24_FLAG_IRUGO,
> + at24_read_post_vaio);
> AT24_CHIP_DATA(at24_data_24c04, 4096 / 8, 0);
> AT24_CHIP_DATA(at24_data_24cs04, 16,
> AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
> @@ -177,6 +211,7 @@ static const struct i2c_device_id at24_i
> { "24mac402", (kernel_ulong_t)&at24_data_24mac402 },
> { "24mac602", (kernel_ulong_t)&at24_data_24mac602 },
> { "spd", (kernel_ulong_t)&at24_data_spd },
> + { "24c02-vaio", (kernel_ulong_t)&at24_data_24c02_vaio },
> { "24c04", (kernel_ulong_t)&at24_data_24c04 },
> { "24cs04", (kernel_ulong_t)&at24_data_24cs04 },
> { "24c08", (kernel_ulong_t)&at24_data_24c08 },
> @@ -389,6 +424,9 @@ static int at24_read(void *priv, unsigne
> struct device *dev;
> char *buf = val;
> int ret;
> + unsigned int orig_off = off;
> + char *orig_buf = buf;
> + size_t orig_count = count;
>
> at24 = priv;
> dev = at24_base_client_dev(at24);
> @@ -427,6 +465,9 @@ static int at24_read(void *priv, unsigne
>
> pm_runtime_put(dev);
>
> + if (unlikely(at24->read_post))
> + at24->read_post(orig_off, orig_buf, orig_count);
> +
> return 0;
> }
>
> @@ -654,6 +695,7 @@ static int at24_probe(struct i2c_client
> at24->byte_len = byte_len;
> at24->page_size = page_size;
> at24->flags = flags;
> + at24->read_post = cdata->read_post;
> at24->num_addresses = num_addresses;
> at24->offset_adj = at24_get_offset_adj(flags, byte_len);
> at24->client[0].client = client;
>
>
> --
> Jean Delvare
> SUSE L3 Support
Looks good to me, I can take it after v5.9-rc1 is tagged.
Bartosz
