Messages in this thread | | | Date | Fri, 26 Sep 2014 17:00:41 -0500 | From | Chuck Ebbert <> | Subject | Re: [PATCH] x86 : Ensure X86_FLAGS_NT is cleared on syscall entry |
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On Thu, 25 Sep 2014 12:42:51 -0700 Anish Bhatt <anish@chelsio.com> wrote:
> The MSR_SYSCALL_MASK, which is responsible for clearing specific EFLAGS on > syscall entry, should also clear the nested task (NT) flag to be safe from > userspace injection. Without this fix the application segmentation > faults on syscall return because of the changed meaning of the IRET > instruction. > > Further details can be seen here https://bugs.winehq.org/show_bug.cgi?id=33275 > > Signed-off-by: Anish Bhatt <anish@chelsio.com> > Signed-off-by: Sebastian Lackner <sebastian@fds-team.de> > --- > arch/x86/kernel/cpu/common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index e4ab2b4..3126558 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -1184,7 +1184,7 @@ void syscall_init(void) > /* Flags to clear on syscall */ > wrmsrl(MSR_SYSCALL_MASK, > X86_EFLAGS_TF|X86_EFLAGS_DF|X86_EFLAGS_IF| > - X86_EFLAGS_IOPL|X86_EFLAGS_AC); > + X86_EFLAGS_IOPL|X86_EFLAGS_AC|X86_EFLAGS_NT); > } > > /*
I don't get it. Why isn't this patch acceptable, at least on x86-64 where NT is never valid?
Bueller?
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