[Bug 3410] New: Since 8.9p1 MaxStartups >=1024, in sshd_config, causes "error: ppoll: Invalid argument"

bugzilla-daemon at mindrot.org bugzilla-daemon at mindrot.org
Tue Mar 22 01:24:54 AEDT 2022


            Bug ID: 3410
           Summary: Since 8.9p1 MaxStartups >=1024, in sshd_config, causes
                    "error: ppoll: Invalid argument"
           Product: Portable OpenSSH
           Version: 8.9p1
          Hardware: amd64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: sshd
          Assignee: unassigned-bugs at mindrot.org
          Reporter: for.github.20200406 at gmx.de

Up to 8.8p1 a value of 4096 for MaxStartups in sshd_config was no
Since 8.9p1 switched to usage of ppoll(2) the maximum value for
MaxStartups is 1023.

Because this is default ppoll(2) behavior, the expected behavior of
sshd would be:
- the documentation should be updated
- sshd -t should show MaxStartups > 1023 as problem (would have saved
me some time, to identify MaxStartups as problem)
- maybe a MaxStartups > 1023 should be reduced to 1023 internally

PS: Maybe setting such a high value for MaxStartups is the wrong
approach for e.g. allowing a massive threaded app access via ssh, but
it was a working solution (in reality, I had a problem with ~100
unauthenticated connections, setting it to 1023 will be good enough).

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