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Subject[tip:x86/setup] x86, setup: Fix EDD3.0 data verification.
Commit-ID:  0c61227094b3ddaca2f847ee287c4a2e3762b5a2
Gitweb: http://git.kernel.org/tip/0c61227094b3ddaca2f847ee287c4a2e3762b5a2
Author: Gleb Natapov <gleb@redhat.com>
AuthorDate: Tue, 26 Apr 2011 11:21:32 +0300
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Wed, 27 Apr 2011 14:16:12 -0700

x86, setup: 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>
Link: http://lkml.kernel.org/r/20110426082132.GG2265@redhat.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
drivers/firmware/edd.c | 22 +++++++++++-----------
1 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/drivers/firmware/edd.c b/drivers/firmware/edd.c
index 96c25d9..f1b7f65 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 +544,16 @@ 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) {
+
+ /* We support only T13 spec */
+ if (info->params.device_path_info_length != 44)
+ return 0;
+
+ for (i = 30; i < info->params.device_path_info_length + 30; i++)
+ csum += *(((u8 *)&info->params) + i);
+
+ if (csum)
return 0;
- }

return 1;
}

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