We need to check that device paths provided via UEFI variables are not malformed.
Provide function efi_dp_check_length() to check if a device path has an end node within a given number of bytes.
Signed-off-by: Heinrich Schuchardt xypron.glpk@gmx.de --- include/efi_loader.h | 2 ++ lib/efi_loader/efi_device_path.c | 33 ++++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+)
diff --git a/include/efi_loader.h b/include/efi_loader.h index 50a17a33ca..0baa1d2324 100644 --- a/include/efi_loader.h +++ b/include/efi_loader.h @@ -631,6 +631,8 @@ efi_status_t efi_dp_from_name(const char *dev, const char *devnr, const char *path, struct efi_device_path **device, struct efi_device_path **file); +ssize_t efi_dp_check_length(const struct efi_device_path *dp, + const size_t maxlen);
#define EFI_DP_TYPE(_dp, _type, _subtype) \ (((_dp)->type == DEVICE_PATH_TYPE_##_type) && \ diff --git a/lib/efi_loader/efi_device_path.c b/lib/efi_loader/efi_device_path.c index 7ae14f3423..8a5c13c424 100644 --- a/lib/efi_loader/efi_device_path.c +++ b/lib/efi_loader/efi_device_path.c @@ -1127,3 +1127,36 @@ efi_status_t efi_dp_from_name(const char *dev, const char *devnr,
return EFI_SUCCESS; } + +/** + * efi_dp_check_length() - check length of a device path + * + * @dp: pointer to device path + * @maxlen: maximum length of the device path + * Return: + * * length of the device path if it is less or equal @maxlen + * * -1 if the device path is longer then @maxlen + * * -1 if a device path node has a length of less than 4 + * * -EINVAL if maxlen exceeds SSIZE_MAX + */ +ssize_t efi_dp_check_length(const struct efi_device_path *dp, + const size_t maxlen) +{ + ssize_t ret = 0; + u16 len; + + if (maxlen > SSIZE_MAX) + return -EINVAL; + for (;;) { + len = dp->length; + if (len < 4) + return -1; + ret += len; + if (ret > maxlen) + return -1; + if (dp->type == DEVICE_PATH_TYPE_END && + dp->sub_type == DEVICE_PATH_SUB_TYPE_END) + return ret; + dp = (const struct efi_device_path *)((const u8 *)dp + len); + } +} -- 2.28.0