As suggested by Marc and Lorenzo, first we need to check whether the
platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
de-referencing what it points at to detect the length of the platform
timer struct and then check that the length of current platform_timer
struct is also valid, i.e. the length is not zero and within gtdt_end.
Now next_platform_timer() only checks against gtdt_end for the entry of
subsequent platform timer without checking the length of it and will
not report error if the check failed and the existing check in function
acpi_gtdt_init() is also not enough.
Modify the for_each_platform_timer() iterator and use it combined with
a dedicated check function platform_timer_valid() to do the check
against table length (gtdt_end) for each element of platform timer
array in function acpi_gtdt_init(), making sure that both their entry
and length actually fit in the table.
Suggested-by: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>
Co-developed-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Zheng Zengkai <zhengzengkai@xxxxxxxxxx>
---
Changes in v4:
- remove the tmp pointer to make the code more concise.
Changes in v3:
- based on Marc's patch and reuse the for_each_platform_timer() loop
Link to v3: https://lore.kernel.org/linux-arm-kernel/20241015152602.184108-1-zhengzengkai@xxxxxxxxxx/
Changes in v2:
- Check against gtdt_end for both entry and len of each array element
Link to v2: https://lore.kernel.org/linux-arm-kernel/20241012085343.6594-1-zhengzengkai@xxxxxxxxxx/
Link to v1: https://lore.kernel.org/all/20241010144703.113728-1-zhengzengkai@xxxxxxxxxx/
Link to previous related patches:
https://lore.kernel.org/all/20241008082429.33646-1-zhengzengkai@xxxxxxxxxx/
https://lore.kernel.org/all/20240930030716.179992-1-zhengzengkai@xxxxxxxxxx/
---
drivers/acpi/arm64/gtdt.c | 29 ++++++++++++++++++++---------
1 file changed, 20 insertions(+), 9 deletions(-)
diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
index c0e77c1c8e09..d7c4e1b9915b 100644
--- a/drivers/acpi/arm64/gtdt.c
+++ b/drivers/acpi/arm64/gtdt.c
@@ -36,19 +36,25 @@ struct acpi_gtdt_descriptor {
static struct acpi_gtdt_descriptor acpi_gtdt_desc __initdata;
-static inline __init void *next_platform_timer(void *platform_timer)
+static __init bool platform_timer_valid(void *platform_timer)
{
struct acpi_gtdt_header *gh = platform_timer;
- platform_timer += gh->length;
- if (platform_timer < acpi_gtdt_desc.gtdt_end)
- return platform_timer;
+ return (platform_timer >= (void *)(acpi_gtdt_desc.gtdt + 1) &&
+ platform_timer < acpi_gtdt_desc.gtdt_end &&
+ gh->length != 0 &&
+ platform_timer + gh->length <= acpi_gtdt_desc.gtdt_end);
+}
+
+static __init void *next_platform_timer(void *platform_timer)
+{
+ struct acpi_gtdt_header *gh = platform_timer;
- return NULL;
+ return platform_timer + gh->length;
}
#define for_each_platform_timer(_g) \
- for (_g = acpi_gtdt_desc.platform_timer; _g; \
+ for (_g = acpi_gtdt_desc.platform_timer; platform_timer_valid(_g);\
_g = next_platform_timer(_g))
static inline bool is_timer_block(void *platform_timer)
@@ -157,6 +163,7 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
{
void *platform_timer;
struct acpi_table_gtdt *gtdt;
+ int cnt = 0;
gtdt = container_of(table, struct acpi_table_gtdt, header);
acpi_gtdt_desc.gtdt = gtdt;
@@ -176,12 +183,16 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
return 0;
}
- platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
- if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
+ acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
+ for_each_platform_timer(platform_timer)
+ cnt++;
+
+ if (cnt != gtdt->platform_timer_count) {
+ acpi_gtdt_desc.platform_timer = NULL;
pr_err(FW_BUG "invalid timer data.\n");
return -EINVAL;
}
- acpi_gtdt_desc.platform_timer = platform_timer;
+
if (platform_timer_count)
*platform_timer_count = gtdt->platform_timer_count;
--
2.20.1