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 v3: - based on Marc's patch and reuse the for_each_platform_timer() loop 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/ --- drivers/acpi/arm64/gtdt.c | 32 +++++++++++++++++++++----------- 1 file changed, 21 insertions(+), 11 deletions(-) diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c index c0e77c1c8e09..3583c99afb0d 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; \ +#define for_each_platform_timer(_g, first_entry) \ + for (_g = first_entry; platform_timer_valid(_g); \ _g = next_platform_timer(_g)) static inline bool is_timer_block(void *platform_timer) @@ -155,8 +161,9 @@ bool __init acpi_gtdt_c3stop(int type) int __init acpi_gtdt_init(struct acpi_table_header *table, int *platform_timer_count) { - void *platform_timer; + void *platform_timer, *tmp; struct acpi_table_gtdt *gtdt; + int cnt = 0; gtdt = container_of(table, struct acpi_table_gtdt, header); acpi_gtdt_desc.gtdt = gtdt; @@ -177,7 +184,10 @@ int __init acpi_gtdt_init(struct acpi_table_header *table, } platform_timer = (void *)gtdt + gtdt->platform_timer_offset; - if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) { + for_each_platform_timer(tmp, platform_timer) + cnt++; + + if (cnt != gtdt->platform_timer_count) { pr_err(FW_BUG "invalid timer data.\n"); return -EINVAL; } @@ -305,7 +315,7 @@ int __init acpi_arch_timer_mem_init(struct arch_timer_mem *timer_mem, void *platform_timer; *timer_count = 0; - for_each_platform_timer(platform_timer) { + for_each_platform_timer(platform_timer, acpi_gtdt_desc.platform_timer) { if (is_timer_block(platform_timer)) { ret = gtdt_parse_timer_block(platform_timer, timer_mem); if (ret) @@ -398,7 +408,7 @@ static int __init gtdt_sbsa_gwdt_init(void) if (ret || !timer_count) goto out_put_gtdt; - for_each_platform_timer(platform_timer) { + for_each_platform_timer(platform_timer, acpi_gtdt_desc.platform_timer) { if (is_non_secure_watchdog(platform_timer)) { ret = gtdt_import_sbsa_gwdt(platform_timer, gwdt_count); if (ret) -- 2.20.1
