In openbsd-compat/bsd-pselect.c file in pselect() function. Line 196 incorrect call to select() function. If unmasked !=0 , nfds need +1 8 if (unmasked) { 7 pselect_notify_setup(); 6 pselect_notify_prepare(readfds); 5 nfds = MAX(nfds, notify_pipe[0]); 4 } 3 2 /* Unmask signals, call select then restore signal mask. */ 1 sigprocmask(SIG_SETMASK, mask, &osig); 196 ret = select(nfds, readfds, writefds, exceptfds, tvp); 1 saved_errno = errno; 2 sigprocmask(SIG_SETMASK, &osig, NULL); 3 4 if (unmasked) 5 pselect_notify_done(readfds);
(In reply to Yaroslav from comment #0) > In openbsd-compat/bsd-pselect.c file in pselect() function. > > Line 196 incorrect call to select() function. > If unmasked !=0 , nfds need +1 For the common case nfds should already have the 1 added by the caller, eg in sshd.c: /* Wait until a connection arrives or a child exits. */ ret = pselect(maxfd+1, fdset, NULL, NULL, NULL, &osigset); I could see this being a problem in the case where notify_pipe[0] is higher than any descriptor in the fdsets, in which case I think the +1 should be added to notify_pipe[0]: nfds = MAX(nfds, notify_pipe[0]+1); Would that solve the problem? Also, out of curiosity, what platform is this (you indicated "Other")?
I added the following code and it solved the problem 200 nfds = MAX(nfds, notify_pipe[0]); 201 ++nfds; I am porting OpenSSH to OpenVMS.
(In reply to Yaroslav from comment #2) > I added the following code and it solved the problem > > 200 nfds = MAX(nfds, notify_pipe[0]); > 201 ++nfds; As I described above I don't think that's correct. In the case where nfds was not increased in the MAX(), nfds is being incremented twice which may cause other problems. The code I suggested does not do that. Does it also fix the problem?
(In reply to Darren Tucker from comment #3) > (In reply to Yaroslav from comment #2) > > I added the following code and it solved the problem > > > > 200 nfds = MAX(nfds, notify_pipe[0]); > > 201 ++nfds; > > As I described above I don't think that's correct. In the case > where nfds was not increased in the MAX(), nfds is being incremented > twice which may cause other problems. > > The code I suggested does not do that. Does it also fix the problem? I tested on 5 connections everything works correctly. But I agree that nfsd contains information about the number of file descriptors, and MAX will check the maximum descriptor if (unmasked) { pselect_notify_setup(); pselect_notify_prepare(readfds); --nfds; nfds = MAX(nfds, notify_pipe[0]); ++nfds; }
Thanks, I have committed the fix and cherry-picked it into the 8.7 branch so it will be in the next release.
closing bugs resolved before openssh-8.9