On 2020/5/4 15:36, Ard Biesheuvel wrote:
On Mon, 4 May 2020 at 06:32, Hanjun Guo <guohanjun@xxxxxxxxxx> wrote:
On 2020/5/2 0:10, Ard Biesheuvel wrote:
The ID mapping table structure of the IORT table describes the size of
a range using a num_ids field carrying the number of IDs in the region
minus one. This has been misinterpreted in the past in the parsing code,
and firmware is known to have shipped where this results in an ambiguity,
where regions that should be adjacent have an overlap of one value.
So let's work around this by detecting this case specifically: when
resolving an ID translation, allow one that matches right at the end of
a multi-ID region to be superseded by a subsequent one.
To prevent potential regressions on broken firmware that happened to
work before, only take the subsequent match into account if it occurs
at the start of a mapping region.
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
drivers/acpi/arm64/iort.c | 40 +++++++++++++++++---
1 file changed, 34 insertions(+), 6 deletions(-)
diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 98be18266a73..9f139a94a1d3 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -300,7 +300,7 @@ static acpi_status iort_match_node_callback(struct acpi_iort_node *node,
}
static int iort_id_map(struct acpi_iort_id_mapping *map, u8 type, u32 rid_in,
- u32 *rid_out)
+ u32 *rid_out, bool check_overlap)
{
/* Single mapping does not care for input id */
if (map->flags & ACPI_IORT_ID_SINGLE_MAPPING) {
@@ -316,10 +316,34 @@ static int iort_id_map(struct acpi_iort_id_mapping *map, u8 type, u32 rid_in,
}
if (rid_in < map->input_base ||
- (rid_in >= map->input_base + map->id_count))
+ (rid_in > map->input_base + map->id_count))
return -ENXIO;
+ if (check_overlap) {
+ /*
+ * We already found a mapping for this input ID at the end of
+ * another region. If it coincides with the start of this
+ * region, we assume the prior match was due to the off-by-1
+ * issue mentioned below, and allow it to be superseded.
+ * Otherwise, things are *really* broken, and we just disregard
+ * duplicate matches entirely to retain compatibility.
+ */
+ pr_err(FW_BUG "[map %p] conflicting mapping for input ID 0x%x\n",
+ map, rid_in);
As we already applied a workaround here, can we add "applying
workaround" in the error message? This will make the customers
less uneasy to see such message in the boot log. Once the product
was deliveried to customers, it's not that easy to update all the
firmwares entirely.
Sure.
Since Will already merged this patchset, I would like to send a patch
on top of it, what do you think?
Thanks
Hanjun
