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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2015-03-28 11:25:04 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-03-28 11:25:04 -0700 |
| commit | 7fc377ecf452c02f3fd6aa0db9a3fd7d012ff500 (patch) | |
| tree | 291dee5351572ec9bc51a0175bc966fd7c2752b3 | |
| parent | 4a89452e70a019cb6bfb1114b12f2607c3bace24 (diff) | |
| parent | b3494a4ab20f6bdf74cdf2badf7918bb65ee8a00 (diff) | |
| download | lwn-7fc377ecf452c02f3fd6aa0db9a3fd7d012ff500.tar.gz lwn-7fc377ecf452c02f3fd6aa0db9a3fd7d012ff500.zip | |
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.S | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 1d74d161687c..2babb393915e 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) |