On 03/28, Andy Lutomirski wrote: > > On Tue, Mar 28, 2017 at 7:54 AM, Oleg Nesterov <[email protected]> wrote: > > get_nr_restart_syscall() checks TS_I386_REGS_POKED but this bit is only > > set if debugger is 32-bit. If a 64-bit debugger restores the registers > > of a 32-bit debugee outside of syscall exit path get_nr_restart_syscall() > > wrongly returns __NR_restart_syscall. > > I had sent a patch that introduced a new syscall nr, but it's not > quite safe because it could break seccomp-using programs.
Ah, indeed... > But your > patch here is also screwy. Yes, yes, it doesn't try to solve all possible problems, I even mentioned this in the changelog. > How about we store the syscall arch to be restored in task_struct > along with restart_block? Yes, perhaps we will have to finally do this. Not really nice too. > the way there without heuristics as nasty as yours. I agree it will be better, but I refuse to treat them as mine checks ;) > P.S. __USER32_CS is the wrong check even if we used your approach. > user_64bit_regs() is much better. Yes, thanks. If only I understood what cs == pv_info.extra_user_64bit_cs actually means... OK, please ignore this patch, I'll try to make another fix. Oleg.
