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Commit 7fc377ec authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 4a89452e b3494a4a

arch/x86/kernel/entry_64.S

+14 −4
Original line number Diff line number Diff line
@@ -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)