3.2-stable review patch. If anyone has any objections, please let me know.
------------------ From: Matthew Garrett <[email protected]> commit 54b3a4d311c98ad94b737802a8b5f2c8c6bfd627 upstream. Ben Hutchings pointed out that the validation in efivars was inadequate - most obviously, an entry with size 0 would server as a DoS against the kernel. Improve this based on his suggestions. Signed-off-by: Matthew Garrett <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> --- drivers/firmware/efivars.c | 46 +++++++++++++++++++++++++++++--------------- 1 file changed, 30 insertions(+), 16 deletions(-) diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c index 891e467..47408e8 100644 --- a/drivers/firmware/efivars.c +++ b/drivers/firmware/efivars.c @@ -192,18 +192,21 @@ utf16_strncmp(const efi_char16_t *a, const efi_char16_t *b, size_t len) } static bool -validate_device_path(struct efi_variable *var, int match, u8 *buffer, int len) +validate_device_path(struct efi_variable *var, int match, u8 *buffer, + unsigned long len) { struct efi_generic_dev_path *node; int offset = 0; node = (struct efi_generic_dev_path *)buffer; - while (offset < len) { - offset += node->length; + if (len < sizeof(*node)) + return false; - if (offset > len) - return false; + while (offset <= len - sizeof(*node) && + node->length >= sizeof(*node) && + node->length <= len - offset) { + offset += node->length; if ((node->type == EFI_DEV_END_PATH || node->type == EFI_DEV_END_PATH2) && @@ -222,7 +225,8 @@ validate_device_path(struct efi_variable *var, int match, u8 *buffer, int len) } static bool -validate_boot_order(struct efi_variable *var, int match, u8 *buffer, int len) +validate_boot_order(struct efi_variable *var, int match, u8 *buffer, + unsigned long len) { /* An array of 16-bit integers */ if ((len % 2) != 0) @@ -232,19 +236,27 @@ validate_boot_order(struct efi_variable *var, int match, u8 *buffer, int len) } static bool -validate_load_option(struct efi_variable *var, int match, u8 *buffer, int len) +validate_load_option(struct efi_variable *var, int match, u8 *buffer, + unsigned long len) { u16 filepathlength; - int i, desclength = 0; + int i, desclength = 0, namelen; + + namelen = utf16_strnlen(var->VariableName, sizeof(var->VariableName)); /* Either "Boot" or "Driver" followed by four digits of hex */ for (i = match; i < match+4; i++) { - if (hex_to_bin(var->VariableName[i] & 0xff) < 0) + if (var->VariableName[i] > 127 || + hex_to_bin(var->VariableName[i] & 0xff) < 0) return true; } - /* A valid entry must be at least 6 bytes */ - if (len < 6) + /* Reject it if there's 4 digits of hex and then further content */ + if (namelen > match + 4) + return false; + + /* A valid entry must be at least 8 bytes */ + if (len < 8) return false; filepathlength = buffer[4] | buffer[5] << 8; @@ -253,7 +265,7 @@ validate_load_option(struct efi_variable *var, int match, u8 *buffer, int len) * There's no stored length for the description, so it has to be * found by hand */ - desclength = utf16_strsize((efi_char16_t *)(buffer + 6), len) + 2; + desclength = utf16_strsize((efi_char16_t *)(buffer + 6), len - 6) + 2; /* Each boot entry must have a descriptor */ if (!desclength) @@ -275,7 +287,8 @@ validate_load_option(struct efi_variable *var, int match, u8 *buffer, int len) } static bool -validate_uint16(struct efi_variable *var, int match, u8 *buffer, int len) +validate_uint16(struct efi_variable *var, int match, u8 *buffer, + unsigned long len) { /* A single 16-bit integer */ if (len != 2) @@ -285,7 +298,8 @@ validate_uint16(struct efi_variable *var, int match, u8 *buffer, int len) } static bool -validate_ascii_string(struct efi_variable *var, int match, u8 *buffer, int len) +validate_ascii_string(struct efi_variable *var, int match, u8 *buffer, + unsigned long len) { int i; @@ -303,7 +317,7 @@ validate_ascii_string(struct efi_variable *var, int match, u8 *buffer, int len) struct variable_validate { char *name; bool (*validate)(struct efi_variable *var, int match, u8 *data, - int len); + unsigned long len); }; static const struct variable_validate variable_validate[] = { @@ -325,7 +339,7 @@ static const struct variable_validate variable_validate[] = { }; static bool -validate_var(struct efi_variable *var, u8 *data, int len) +validate_var(struct efi_variable *var, u8 *data, unsigned long len) { int i; u16 *unicode_name = var->VariableName; -- 1.7.10 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
