diff options
Diffstat (limited to 'drivers/misc/lkdtm')
| -rw-r--r-- | drivers/misc/lkdtm/bugs.c | 39 | ||||
| -rw-r--r-- | drivers/misc/lkdtm/core.c | 3 | ||||
| -rw-r--r-- | drivers/misc/lkdtm/lkdtm.h | 3 | ||||
| -rw-r--r-- | drivers/misc/lkdtm/refcount.c | 11 |
4 files changed, 46 insertions, 10 deletions
diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index 7284a22b1a09..a4fdad04809a 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -12,6 +12,10 @@ #include <linux/sched/task_stack.h> #include <linux/uaccess.h> +#ifdef CONFIG_X86_32 +#include <asm/desc.h> +#endif + struct lkdtm_list { struct list_head node; }; @@ -337,3 +341,38 @@ void lkdtm_UNSET_SMEP(void) pr_err("FAIL: this test is x86_64-only\n"); #endif } + +#ifdef CONFIG_X86_32 +void lkdtm_DOUBLE_FAULT(void) +{ + /* + * Trigger #DF by setting the stack limit to zero. This clobbers + * a GDT TLS slot, which is okay because the current task will die + * anyway due to the double fault. + */ + struct desc_struct d = { + .type = 3, /* expand-up, writable, accessed data */ + .p = 1, /* present */ + .d = 1, /* 32-bit */ + .g = 0, /* limit in bytes */ + .s = 1, /* not system */ + }; + + local_irq_disable(); + write_gdt_entry(get_cpu_gdt_rw(smp_processor_id()), + GDT_ENTRY_TLS_MIN, &d, DESCTYPE_S); + + /* + * Put our zero-limit segment in SS and then trigger a fault. The + * 4-byte access to (%esp) will fault with #SS, and the attempt to + * deliver the fault will recursively cause #SS and result in #DF. + * This whole process happens while NMIs and MCEs are blocked by the + * MOV SS window. This is nice because an NMI with an invalid SS + * would also double-fault, resulting in the NMI or MCE being lost. + */ + asm volatile ("movw %0, %%ss; addl $0, (%%esp)" :: + "r" ((unsigned short)(GDT_ENTRY_TLS_MIN << 3))); + + panic("tried to double fault but didn't die\n"); +} +#endif diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c index cbc4c9045a99..ee0d6e721441 100644 --- a/drivers/misc/lkdtm/core.c +++ b/drivers/misc/lkdtm/core.c @@ -171,6 +171,9 @@ static const struct crashtype crashtypes[] = { CRASHTYPE(USERCOPY_KERNEL_DS), CRASHTYPE(STACKLEAK_ERASING), CRASHTYPE(CFI_FORWARD_PROTO), +#ifdef CONFIG_X86_32 + CRASHTYPE(DOUBLE_FAULT), +#endif }; diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h index ab446e0bde97..c56d23e37643 100644 --- a/drivers/misc/lkdtm/lkdtm.h +++ b/drivers/misc/lkdtm/lkdtm.h @@ -28,6 +28,9 @@ void lkdtm_CORRUPT_USER_DS(void); void lkdtm_STACK_GUARD_PAGE_LEADING(void); void lkdtm_STACK_GUARD_PAGE_TRAILING(void); void lkdtm_UNSET_SMEP(void); +#ifdef CONFIG_X86_32 +void lkdtm_DOUBLE_FAULT(void); +#endif /* lkdtm_heap.c */ void __init lkdtm_heap_init(void); diff --git a/drivers/misc/lkdtm/refcount.c b/drivers/misc/lkdtm/refcount.c index 0a146b32da13..de7c5ab528d9 100644 --- a/drivers/misc/lkdtm/refcount.c +++ b/drivers/misc/lkdtm/refcount.c @@ -6,14 +6,6 @@ #include "lkdtm.h" #include <linux/refcount.h> -#ifdef CONFIG_REFCOUNT_FULL -#define REFCOUNT_MAX (UINT_MAX - 1) -#define REFCOUNT_SATURATED UINT_MAX -#else -#define REFCOUNT_MAX INT_MAX -#define REFCOUNT_SATURATED (INT_MIN / 2) -#endif - static void overflow_check(refcount_t *ref) { switch (refcount_read(ref)) { @@ -127,7 +119,7 @@ void lkdtm_REFCOUNT_DEC_ZERO(void) static void check_negative(refcount_t *ref, int start) { /* - * CONFIG_REFCOUNT_FULL refuses to move a refcount at all on an + * refcount_t refuses to move a refcount at all on an * over-sub, so we have to track our starting position instead of * looking only at zero-pinning. */ @@ -210,7 +202,6 @@ static void check_from_zero(refcount_t *ref) /* * A refcount_inc() from zero should pin to zero or saturate and may WARN. - * Only CONFIG_REFCOUNT_FULL provides this protection currently. */ void lkdtm_REFCOUNT_INC_ZERO(void) { |