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Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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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
This commit is contained in:
Linus Torvalds 2015-03-28 11:25:04 -07:00
commit 7fc377ecf4
1 changed files with 14 additions and 4 deletions
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18
arch/x86/kernel/entry_64.S
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@ -364,12 +364,21 @@ system_call_fastpath:
* Has incomplete stack frame and undefined top of stack.
*/
ret_from_sys_call:
testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
jnz int_ret_from_sys_call_fixup /* Go the the slow path */
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
/*
* We must check ti flags with interrupts (or at least preemption)
* off because we must *never* return to userspace without
* processing exit work that is enqueued if we're preempted here.
* In particular, returning to userspace with any of the one-shot
* flags (TIF_NOTIFY_RESUME, TIF_USER_RETURN_NOTIFY, etc) set is
* very bad.
*/
testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
jnz int_ret_from_sys_call_fixup /* Go the the slow path */
CFI_REMEMBER_STATE
/*
* sysretq will re-enable interrupts:
@ -386,7 +395,7 @@ ret_from_sys_call:
int_ret_from_sys_call_fixup:
FIXUP_TOP_OF_STACK %r11, -ARGOFFSET
jmp int_ret_from_sys_call
jmp int_ret_from_sys_call_irqs_off
/* Do syscall tracing */
tracesys:
@ -432,6 +441,7 @@ tracesys_phase2:
GLOBAL(int_ret_from_sys_call)
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
int_ret_from_sys_call_irqs_off:
movl $_TIF_ALLWORK_MASK,%edi
/* edi: mask to check */
GLOBAL(int_with_check)