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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-12-01 19:05:07 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-12-01 19:05:07 -0800 |
commit | e5b3fc125d768eacd73bb4dc5019f0ce95635af4 (patch) | |
tree | 4f7e06f8a0493865a6b604bbcef5118c4582ebcf /drivers | |
parent | b7fcf31f7036895ca8fc3a30eefffab0e82f75f6 (diff) | |
parent | 91298f1a302dad0f0f630413c812818636faa8a0 (diff) | |
download | linux-e5b3fc125d768eacd73bb4dc5019f0ce95635af4.tar.bz2 |
Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Ingo Molnar:
"Various fixes:
- Fix the PAT performance regression that downgraded write-combining
device memory regions to uncached.
- There's been a number of bugs in 32-bit double fault handling -
hopefully all fixed now.
- Fix an LDT crash
- Fix an FPU over-optimization that broke with GCC9 code
optimizations.
- Misc cleanups"
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mm/pat: Fix off-by-one bugs in interval tree search
x86/ioperm: Save an indentation level in tss_update_io_bitmap()
x86/fpu: Don't cache access to fpu_fpregs_owner_ctx
x86/entry/32: Remove unused 'restore_all_notrace' local label
x86/ptrace: Document FSBASE and GSBASE ABI oddities
x86/ptrace: Remove set_segment_reg() implementations for current
x86/traps: die() instead of panicking on a double fault
x86/doublefault/32: Rewrite the x86_32 #DF handler and unify with 64-bit
x86/doublefault/32: Move #DF stack and TSS to cpu_entry_area
x86/doublefault/32: Rename doublefault.c to doublefault_32.c
x86/traps: Disentangle the 32-bit and 64-bit doublefault code
lkdtm: Add a DOUBLE_FAULT crash type on x86
selftests/x86/single_step_syscall: Check SYSENTER directly
x86/mm/32: Sync only to VMALLOC_END in vmalloc_sync_all()
Diffstat (limited to 'drivers')
-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 |
3 files changed, 45 insertions, 0 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); |