From: Tony Battersby Date: Wed, 11 Feb 2009 21:24:19 +0000 (-0800) Subject: intel-iommu: fix endless "Unknown DMAR structure type" loop X-Git-Tag: v2.6.29-rc7~59^2 X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=commitdiff_plain;h=084eb960e81505680a9963665722d1bfd94af6a7 intel-iommu: fix endless "Unknown DMAR structure type" loop I have a SuperMicro C2SBX motherboard with BIOS revision 1.0b. With vt-d enabled in the BIOS, Linux gets into an endless loop printing "DMAR:Unknown DMAR structure type" when booting. Here is the DMAR ACPI table: DMAR @ 0x7fe86dec 0000: 44 4d 41 52 98 00 00 00 01 6f 49 6e 74 65 6c 20 DMAR.....oIntel 0010: 4f 45 4d 44 4d 41 52 20 00 00 04 06 4c 4f 48 52 OEMDMAR ....LOHR 0020: 01 00 00 00 23 00 00 00 00 00 00 00 00 00 00 00 ....#........... 0030: 01 00 58 00 00 00 00 00 00 a0 e8 7f 00 00 00 00 ..X............. 0040: ff ff ef 7f 00 00 00 00 01 08 00 00 00 00 1d 00 ................ 0050: 01 08 00 00 00 00 1d 01 01 08 00 00 00 00 1d 02 ................ 0060: 01 08 00 00 00 00 1d 07 01 08 00 00 00 00 1a 00 ................ 0070: 01 08 00 00 00 00 1a 01 01 08 00 00 00 00 1a 02 ................ 0080: 01 08 00 00 00 00 1a 07 01 08 00 00 00 00 1a 07 ................ 0090: c0 00 68 00 04 10 66 60 ..h...f` Here are the messages printed by the kernel: DMAR:Host address width 36 DMAR:RMRR base: 0x000000007fe8a000 end: 0x000000007fefffff DMAR:Unknown DMAR structure type DMAR:Unknown DMAR structure type DMAR:Unknown DMAR structure type ... Although I not very familiar with ACPI, to me it looks like struct acpi_dmar_header::length == 0x0058 is incorrect, causing parse_dmar_table() to look at an invalid offset on the next loop. This offset happens to have struct acpi_dmar_header::length == 0x0000, which prevents the loop from ever terminating. This patch checks for this condition and bails out instead of looping forever. Signed-off-by: Tony Battersby Signed-off-by: Andrew Morton Signed-off-by: David Woodhouse --- diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c index 8d3e9c261061..26c536b51c5a 100644 --- a/drivers/pci/dmar.c +++ b/drivers/pci/dmar.c @@ -330,6 +330,14 @@ parse_dmar_table(void) entry_header = (struct acpi_dmar_header *)(dmar + 1); while (((unsigned long)entry_header) < (((unsigned long)dmar) + dmar_tbl->length)) { + /* Avoid looping forever on bad ACPI tables */ + if (entry_header->length == 0) { + printk(KERN_WARNING PREFIX + "Invalid 0-length structure\n"); + ret = -EINVAL; + break; + } + dmar_table_print_dmar_entry(entry_header); switch (entry_header->type) {