Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fix from Ingo Molnar:
"Fix x86 syscall exit code bug that resulted in spurious non-execution
of TIF-driven user-return worklets, causing big trouble for things
like KVM that rely on user notifiers for correctness of their vcpu
model, causing crashes like double faults"
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/asm/entry: Check for syscall exit work with IRQs disabled
+14
-4
+14
-4
arch/x86/kernel/entry_64.S
+14
-4
arch/x86/kernel/entry_64.S
···
364
364
* Has incomplete stack frame and undefined top of stack.
365
365
*/
366
366
ret_from_sys_call:
367
-
testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
368
-
jnz int_ret_from_sys_call_fixup /* Go the the slow path */
369
-
370
367
LOCKDEP_SYS_EXIT
371
368
DISABLE_INTERRUPTS(CLBR_NONE)
372
369
TRACE_IRQS_OFF
370
+
371
+
/*
372
+
* We must check ti flags with interrupts (or at least preemption)
373
+
* off because we must *never* return to userspace without
374
+
* processing exit work that is enqueued if we're preempted here.
375
+
* In particular, returning to userspace with any of the one-shot
376
+
* flags (TIF_NOTIFY_RESUME, TIF_USER_RETURN_NOTIFY, etc) set is
377
+
* very bad.
378
+
*/
379
+
testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
380
+
jnz int_ret_from_sys_call_fixup /* Go the the slow path */
381
+
373
382
CFI_REMEMBER_STATE
374
383
/*
375
384
* sysretq will re-enable interrupts:
···
395
386
396
387
int_ret_from_sys_call_fixup:
397
388
FIXUP_TOP_OF_STACK %r11, -ARGOFFSET
398
-
jmp int_ret_from_sys_call
389
+
jmp int_ret_from_sys_call_irqs_off
399
390
400
391
/* Do syscall tracing */
401
392
tracesys:
···
441
432
GLOBAL(int_ret_from_sys_call)
442
433
DISABLE_INTERRUPTS(CLBR_NONE)
443
434
TRACE_IRQS_OFF
435
+
int_ret_from_sys_call_irqs_off:
444
436
movl $_TIF_ALLWORK_MASK,%edi
445
437
/* edi: mask to check */
446
438
GLOBAL(int_with_check)