Messages in this thread Patch in this message |  | | | Date | Wed, 27 Oct 2010 18:51:12 -0400 | | From | Chris Metcalf <> | | Subject | Re: situation with signals |
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On 10/27/2010 5:37 PM, Al Viro wrote: > On Wed, Oct 27, 2010 at 05:02:10PM -0400, Chris Metcalf wrote >> I set aside this thread to look at when I had a minute, and I believe there >> is just one of the signal issues present in the tile code. The fix is to >> reset regs->fault to something other than the "syscall" fault type when >> exiting from do_signal(), so I'll submit that up for 2.6.37 shortly. > FWIW, I'd do that in handle_signal() when hitting a syscall restart.
Right now I'm just doing it unconditionally in handle_signal()'s caller whether or not I actually call handle_signal, to be paranoid:
@@ -353,11 +353,11 @@ * clear the TS_RESTORE_SIGMASK flag. */ current_thread_info()->status &= ~TS_RESTORE_SIGMASK; } - return; + goto done; } /* Did we come from a system call? */ if (regs->faultnum == INT_SWINT_1) { /* Restart the system call - no handlers present */ @@ -381,10 +381,14 @@ /* If there's no signal to deliver, just put the saved sigmask back. */ if (current_thread_info()->status & TS_RESTORE_SIGMASK) { current_thread_info()->status &= ~TS_RESTORE_SIGMASK; sigprocmask(SIG_SETMASK, ¤t->saved_sigmask, NULL); } + +done: + /* Avoid double syscall restart if there are nested signals. */ + regs->faultnum = INT_SWINT_1_SIGRETURN; }
> BTW, is everything in your pt_regs safe to modify?
What an interesting observation. :-) In fact, it would be possible to overwrite the privilege level (the ex1 register) from within the signal handler and then return to run arbitrary code at kernel PL. I'll fix it.
-- Chris Metcalf, Tilera Corp. http://www.tilera.com
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