Re: [PATCH 3/3] firmware loader: allow distribution to choose defaultsearch paths

[Ming Lei]

On Wed, Jun 5, 2013 at 5:50 PM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> At Wed, 5 Jun 2013 17:35:26 +0800,
> Ming Lei wrote:
>>
>> On Wed, Jun 5, 2013 at 3:10 PM, Takashi Iwai <tiwai@xxxxxxx> wrote:
>> > At Wed,  5 Jun 2013 13:42:49 +0800,
>> > Ming Lei wrote:
>> >>
>> >> For some distributions(e.g. android), firmware images aren't put
>> >> under kernel built-in search paths, so introduce one Kconfig
>> >> option to allow distributions or users to choose its specific default
>> >> search paths, which are always tried before searching from kernel
>> >> built-in paths in direct loading.
>> >>
>> >> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>> >> Cc: Takashi Iwai <tiwai@xxxxxxx>
>> >> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
>> >> ---
>> >>  drivers/base/Kconfig          |   12 +++++++
>> >>  drivers/base/firmware_class.c |   76 ++++++++++++++++++++++++++++++++++++-----
>> >>  2 files changed, 80 insertions(+), 8 deletions(-)
>> >>
>> >> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
>> >> index 07abd9d..5b0c909 100644
>> >> --- a/drivers/base/Kconfig
>> >> +++ b/drivers/base/Kconfig
>> >> @@ -156,6 +156,18 @@ config FW_LOADER_USER_HELPER
>> >>         no longer required unless you have a special firmware file that
>> >>         resides in a non-standard path.
>> >>
>> >> +config FW_CUSTOMIZED_PATH
>> >> +     string "default firmware search paths for direct loading"
>> >> +     help
>> >> +       On some distribution(e.g. android), firmware images aren't
>> >> +       put under kernel built-in search paths, so provide this option
>> >> +       for distributions to choose a distribution specific firmware
>> >> +       search path. The option allows to choose more than one path,
>> >> +       and paths are seperated with semicolon(e.g. on android, the
>> >> +       option might look as "/etc/firmware;/vendor/firmware").
>> >> +
>> >> +       If you are unsure about this, don't choose here.
>> >> +
>> >>  config DEBUG_DRIVER
>> >>       bool "Driver Core verbose debug messages"
>> >>       depends on DEBUG_KERNEL
>> >> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
>> >> index c743409..50b5913 100644
>> >> --- a/drivers/base/firmware_class.c
>> >> +++ b/drivers/base/firmware_class.c
>> >> @@ -267,6 +267,9 @@ static void fw_free_buf(struct firmware_buf *buf)
>> >>  static char fw_path_para[256];
>> >>  static const char * const fw_path[] = {
>> >>       fw_path_para,
>> >> +#ifdef CONFIG_FW_CUSTOMIZED_PATH
>> >> +     CONFIG_FW_CUSTOMIZED_PATH,
>> >> +#endif
>> >>       "/lib/firmware/updates/" UTS_RELEASE,
>> >>       "/lib/firmware/updates",
>> >>       "/lib/firmware/" UTS_RELEASE,
>> >> @@ -314,6 +317,59 @@ static bool fw_read_file_contents(struct file *file, struct firmware_buf *fw_buf
>> >>       return true;
>> >>  }
>> >>
>> >> +static bool fw_get_file_firmware(const char *path,
>> >> +                              struct firmware_buf *buf)
>> >> +{
>> >> +     struct file *file;
>> >> +     bool success;
>> >> +
>> >> +     file = filp_open(path, O_RDONLY, 0);
>> >> +     if (IS_ERR(file))
>> >> +             return false;
>> >> +     success = fw_read_file_contents(file, buf);
>> >> +     fput(file);
>> >> +
>> >> +     return success;
>> >> +}
>> >> +
>> >> +#ifdef CONFIG_FW_CUSTOMIZED_PATH
>> >> +/* The path in @paths is seperated by ';' */
>> >> +static bool fw_get_fw_file_from_paths(const char *paths, char *path,
>> >> +                                   struct firmware_buf *buf)
>> >> +{
>> >> +     int len, start, end;
>> >> +     char *pos;
>> >> +
>> >> +     end = -1;
>> >> +     do {
>> >> +             start = end + 1;
>> >> +             pos = strchr(&paths[start], ';');
>> >> +             if (pos) {
>> >> +                     end = (int)(pos - paths);
>> >> +                     len = end - start;
>> >> +             } else {
>> >> +                     len = strlen(&paths[start]);
>> >> +             }
>> >> +
>> >> +             if (PATH_MAX < len + strlen(buf->fw_id))
>> >> +                     continue;
>> >> +             strncpy(path, &paths[start], len);
>> >> +             snprintf(&path[len], PATH_MAX - len, "/%s", buf->fw_id);
>> >> +
>> >> +             if (fw_get_file_firmware(path, buf))
>> >> +                     return true;
>> >> +     } while (pos && end < strlen(paths) - 1);
>> >> +
>> >> +     return false;
>> >> +}
>> >> +#else
>> >> +static bool fw_get_fw_file_from_paths(const char *paths, char *path,
>> >> +                                   struct firmware_buf *buf)
>> >> +{
>> >> +     return false;
>> >> +}
>> >> +#endif
>> >> +
>> >>  static bool fw_get_filesystem_firmware(struct device *device,
>> >>                                      struct firmware_buf *buf)
>> >>  {
>> >> @@ -322,19 +378,23 @@ static bool fw_get_filesystem_firmware(struct device *device,
>> >>       char *path = __getname();
>> >>
>> >>       for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
>> >> -             struct file *file;
>> >>
>> >>               /* skip the unset customized path */
>> >>               if (!fw_path[i][0])
>> >>                       continue;
>> >>
>> >> -             snprintf(path, PATH_MAX, "%s/%s", fw_path[i], buf->fw_id);
>> >> -
>> >> -             file = filp_open(path, O_RDONLY, 0);
>> >> -             if (IS_ERR(file))
>> >> -                     continue;
>> >> -             success = fw_read_file_contents(file, buf);
>> >> -             fput(file);
>> >> +             /*
>> >> +              * If CONFIG_FW_CUSTOMIZED_PATH is set, search from
>> >> +              * these paths first
>> >> +              */
>> >> +             if (i == 1 && ARRAY_SIZE(fw_path) > 5) {
>> >> +                     success = fw_get_fw_file_from_paths(fw_path[1],
>> >> +                                                         path, buf);
>> >> +             } else {
>> >> +                     snprintf(path, PATH_MAX, "%s/%s", fw_path[i],
>> >> +                              buf->fw_id);
>> >> +                     success = fw_get_file_firmware(path, buf);
>> >
>> > Shouldn't fw_get_fw_file_from_paths() be applied unconditionally?
>> > It'll be benefit for the customized path passed via module option,
>> > too.  The only drawback is a slight code growth, but the code can be
>> > reduced a bit with strcspn() or such.
>>
>> You mean that both the 1st two items should be covered by
>> fw_get_fw_file_from_paths()? If so, the function may become
>> a bit ugly since two strings are required to pass in, and we can't
>> merge one runtime string and one ro string created in compiling.
>
> I meant to simply call fw_get_fw_file_from_paths() for all fw_path[]
> entries.  So far, the module option can pass only a single path.
> But if it's handled through fw_get_file_from_paths(), you can pass
> multiple paths there, too.
>
>> Looks we can let fw_get_fw_file_from_paths() handle all
>> predefined paths(CONFIG_FW_CUSTOMIZED_PATH and
>> kernel built-in paths), then fw_get_filesystem_firmware()
>> may become simple, just check fw_path_para and all
>> other paths by fw_get_fw_file_from_paths(). How about the
>> idea?
>>
>> > BTW, I now wonder what happens if you pass a relative path.
>> > Did you already test it?
>>
>> I tested absolute paths, and not test relative paths. Do you mean
>> it may cause security problem?
>
> Yes.  It just came to my mind while reviewing your patch.
>
>> If so, we can check and ignore them,
>> but it should be OK since the paths are provided by kernel builder.
>> >From view of function, I don't think there are much difference with
>> absolute paths.
>
> The path can be provided via module option, too, so we need to check
> it in anyway.

Yes, even the firmware name may includes "..".


Thanks,
--
Ming Lei
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