Re: [PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

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Gentle ping.

This patch still can be applied to upstream now.

Thanks!


在 2024/10/16 18:01, Lorenzo Pieralisi 写道:
On Wed, Oct 16, 2024 at 05:54:58PM +0800, Zheng Zengkai wrote:
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(-)
Reviewed-by: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>

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

.





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