Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 21 May 2019 09:25:51 +0000 Eric Wong <e@xxxxxxxxx> wrote: > > > Deepa Dinamani <deepa.kernel@xxxxxxxxx> wrote: > > > For all the syscalls that receive a sigmask from the userland, > > > the user sigmask is to be in effect through the syscall execution. > > > At the end of syscall, sigmask of the current process is restored > > > to what it was before the switch over to user sigmask. > > > But, for this to be true in practice, the sigmask should be restored > > > only at the the point we change the saved_sigmask. Anything before > > > that loses signals. And, anything after is just pointless as the > > > signal is already lost by restoring the sigmask. > > > > > > The inherent issue was detected because of a regression caused by > > > 854a6ed56839a. > > > The patch moved the signal_pending() check closer to restoring of the > > > user sigmask. But, it failed to update the error code accordingly. > > > > > > Detailed issue discussion permalink: > > > https://lore.kernel.org/linux-fsdevel/20190427093319.sgicqik2oqkez3wk@dcvr/ > > > > > > Note that the patch returns interrupted errors (EINTR, ERESTARTNOHAND, > > > etc) only when there is no other error. If there is a signal and an error > > > like EINVAL, the syscalls return -EINVAL rather than the interrupted > > > error codes. > > > > > > The sys_io_uring_enter() seems to be returning success when there is > > > a signal and the queue is not empty. This seems to be a bug. I will > > > follow up with a separate patch for that. > > > > > > Reported-by: Eric Wong <e@xxxxxxxxx> > > > Fixes: 854a6ed56839a40f6b5d02a2962f48841482eec4 ("signal: Add restore_user_sigmask()") > > > Signed-off-by: Deepa Dinamani <deepa.kernel@xxxxxxxxx> > > > Reviewed-by: Davidlohr Bueso <dbueso@xxxxxxx> > > (top-posting fixed). > > > It's been 2 weeks and this fix hasn't appeared in mmots / mmotm. > > I also noticed it's missing Cc: for stable@ (below) > > Why is a -stable backport needed? I see some talk above about lost > signals but it is unclear whether these are being observed after fixing > the regression caused by 854a6ed56839a. I guess Deepa's commit messages wasn't clear... I suggest prepending this as the first paragraph to Deepa's original message: This fixes a bug introduced with 854a6ed56839a which caused EINTR to not be reported to userspace on epoll_pwait. Failure to report EINTR to userspace caused problems with user code which relies on EINTR to run signal handlers. > IOW, can we please have a changelog which has a clear and complete > description of the user-visible effects of the change. > > And please Cc Oleg.
