ret_from_fork checks TIF_IA32 to determine whether pt_regs and the related state make sense for ret_from_sys_call. This is entirely the wrong check. TS_COMPAT would make a little more sense, but there's really no point in keeping this optimization at all.
This fixes a return to the wrong user CS if we came from int 0x80 in a 64-bit task. Acked-by: Ingo Molnar <[email protected]> Signed-off-by: Andy Lutomirski <[email protected]> --- arch/x86/kernel/entry_64.S | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 4670fcdb5150..519498d1c8ec 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -550,11 +550,14 @@ ENTRY(ret_from_fork) testl $3,CS(%rsp) # from kernel_thread? jz 1f - testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET - jnz int_ret_from_sys_call - - RESTORE_TOP_OF_STACK %rdi - jmp ret_from_sys_call # go to the SYSRET fastpath + /* + * By the time we get here, we have no idea whether our pt_regs, + * ti flags, and ti status came from the 64-bit SYSCALL fast path, + * the slow path, or one of the ia32entry paths. + * Use int_ret_from_sys_call to return, since it can safely handle + * all of the above. + */ + jmp int_ret_from_sys_call 1: movq %rbp, %rdi -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
