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
