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Subject[PATCH] Fix EDD3.0 data verification.
Check for nonzero path in edd_has_edd30() has no sense. First, it looks
at the wrong memory. Device path starts at offset 30 of the info->params
structure which is at offset 8 from the beginning of info structure, but
code looks at info + 4 instead. This was correct when code was introduced,
but around v2.6.4 three more fields were added to edd_info structure
(commit 66b61a5c in history.git). Second, even if it will check correct
memory it will always succeed since at offset 30 (params->key) there will
be non-zero values otherwise previous check would fail.

The patch replaces this bogus check with one that verifies checksum.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/boot/edd.c b/arch/x86/boot/edd.c
index c501a5b..6c1ac02 100644
--- a/arch/x86/boot/edd.c
+++ b/arch/x86/boot/edd.c
@@ -97,6 +97,13 @@ static int get_edd_info(u8 devno, struct edd_info *ei)

/* Extended Get Device Parameters */

+ /*
+ * The sum of bytes 30-73 in params structure should be zero after
+ * int13 call. Set them to 1 to catch the case when bios works
+ * according to phoenix spec and return 66 bytes. If we left them
+ * to be zero, checksum will not catch that data is in wrong format.
+ */
+ memset(&ei->params.key, 1, 74);
ei->params.length = sizeof(ei->params);
ireg.ah = 0x48;
ireg.si = (size_t)&ei->params;
diff --git a/drivers/firmware/edd.c b/drivers/firmware/edd.c
index 96c25d9..5e3baac 100644
--- a/drivers/firmware/edd.c
+++ b/drivers/firmware/edd.c
@@ -531,8 +531,8 @@ static int
edd_has_edd30(struct edd_device *edev)
{
struct edd_info *info;
- int i, nonzero_path = 0;
- char c;
+ int i;
+ u8 csum = 0;

if (!edev)
return 0;
@@ -544,16 +544,11 @@ edd_has_edd30(struct edd_device *edev)
return 0;
}

- for (i = 30; i <= 73; i++) {
- c = *(((uint8_t *) info) + i + 4);
- if (c) {
- nonzero_path++;
- break;
- }
- }
- if (!nonzero_path) {
+ for (i = 30; i <= 73; i++)
+ csum += *(((u8 *)&info->params) + i);
+
+ if (csum)
return 0;
- }

return 1;
}
--
Gleb.

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