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 <an...@chelsio.com> Signed-off-by: Sebastian Lackner <sebast...@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); } /* -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
