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authorMatthew Garrett <mjg@redhat.com>2012-05-03 16:50:46 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-05-07 08:56:38 -0700
commitecc53109a021559a49beb81c9c4c859012ee975e (patch)
treeaf0bceb7778e6a23bfff8075e6f8408bb06d7b06
parent173c412ef8f37d781eb90f5cc8eeab118b987e68 (diff)
efivars: Improve variable validation
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 <mjg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/firmware/efivars.c46
1 files changed, 30 insertions, 16 deletions
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index a15c0d45f0a3..e27d56c7cc19 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -167,18 +167,21 @@ utf16_strsize(efi_char16_t *data, unsigned long maxlength)
}
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) &&
@@ -197,7 +200,8 @@ 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)
@@ -207,19 +211,27 @@ 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;
@@ -228,7 +240,7 @@ 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)
@@ -250,7 +262,8 @@ 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)
@@ -260,7 +273,8 @@ 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;
@@ -278,7 +292,7 @@ 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[] = {
@@ -300,7 +314,7 @@ 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;