Messages in this thread Patch in this message | | | Date | Wed, 2 Feb 2011 13:21:39 +0200 | From | Gleb Natapov <> | 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.
| |