On Mon, Sep 26, 2016 at 4:49 AM, Wanpeng Li <kernel...@gmail.com> wrote: > From: Wanpeng Li <wanpeng...@hotmail.com> > > WARNING: CPU: 0 PID: 3331 at arch/x86/entry/common.c:45 > enter_from_user_mode+0x32/0x50 > CPU: 0 PID: 3331 Comm: ldt_gdt_64 Not tainted 4.8.0-rc7+ #13 > Call Trace: > dump_stack+0x99/0xd0 > __warn+0xd1/0xf0 > warn_slowpath_null+0x1d/0x20 > enter_from_user_mode+0x32/0x50 > error_entry+0x6d/0xc0 > ? general_protection+0x12/0x30 > ? native_load_gs_index+0xd/0x20 > ? do_set_thread_area+0x19c/0x1f0 > SyS_set_thread_area+0x24/0x30 > do_int80_syscall_32+0x7c/0x220 > entry_INT80_compat+0x38/0x50 > > This can be reproduced by running the GS testcase of ldt_gdt test unit in > selftests. > > do_int80_syscall_32() will call enter_form_user_mode() to convert context > tracking state from user state to kernel state. The load_gs_index can fail > with user gsbase, gsbase will be fixed up and proceed if this happen. > However, enter_from_user_mode() will be called again in the fixed up path > though it is context tracking kernel state currently. > > This patch fix it by just fixing up gsbase and telling lockdep that IRQs > are off once load_gs_index failed with user gsbase. > > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Ingo Molnar <mi...@redhat.com> > Cc: "H. Peter Anvin" <h...@zytor.com> > Cc: Andy Lutomirski <l...@kernel.org> > Cc: Borislav Petkov <b...@alien8.de> > Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com> > --- > arch/x86/entry/entry_64.S | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index d172c61..dc1ec23 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1045,7 +1045,9 @@ ENTRY(error_entry) > * gsbase and proceed. We'll fix up the exception and land in > * .Lgs_change's error handler with kernel gsbase. > */ > - jmp .Lerror_entry_from_usermode_swapgs > + SWAPGS > + TRACE_IRQS_OFF
Let's make this more readable: can you change this to: SWAPGS jmp .Lerror_entry_done and remove the .Lerror_entry_from_usermode_swapgs label as well? Thanks, Andy -- Andy Lutomirski AMA Capital Management, LLC