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authorLinus Torvalds <torvalds@linux-foundation.org>2015-03-28 11:25:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-03-28 11:25:04 -0700
commit7fc377ecf452c02f3fd6aa0db9a3fd7d012ff500 (patch)
tree291dee5351572ec9bc51a0175bc966fd7c2752b3
parent4a89452e70a019cb6bfb1114b12f2607c3bace24 (diff)
parentb3494a4ab20f6bdf74cdf2badf7918bb65ee8a00 (diff)
downloadlinux-7fc377ecf452c02f3fd6aa0db9a3fd7d012ff500.tar.gz
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
-rw-r--r--arch/x86/kernel/entry_64.S18
1 files changed, 14 insertions, 4 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 1d74d161687..2babb393915 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -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)