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Bug 1897712 - openssh SIGSYS on connection attempt
Summary: openssh SIGSYS on connection attempt
Alias: None
Product: Fedora
Classification: Fedora
Component: openssh
Version: rawhide
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
Assignee: Jakub Jelen
QA Contact: Fedora Extras Quality Assurance
Depends On:
Blocks: ARMTracker
TreeView+ depends on / blocked
Reported: 2020-11-13 20:47 UTC by Paul Whalen
Modified: 2020-11-27 01:22 UTC (History)
7 users (show)

Fixed In Version: openssh-8.4p1-3.fc33
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed: 2020-11-27 01:22:51 UTC
Type: Bug

Attachments (Terms of Use)
sshd backtrace (3.23 KB, text/plain)
2020-11-13 20:49 UTC, Paul Whalen
no flags Details

System ID Private Priority Status Summary Last Updated
OpenSSH Project 3232 0 None None None 2020-11-19 10:39:25 UTC

Description Paul Whalen 2020-11-13 20:47:09 UTC
Description of problem:

Attempting to ssh to an armhfp system running rawhide(f34) fails:

ssh root.122.82
Connection reset by port 22

coredumpctl info
           PID: 10183 (sshd)
           UID: 74 (sshd)
           GID: 74 (sshd)
        Signal: 31 (SYS)
     Timestamp: Fri 2020-11-13 15:34:15 EST (27s ago)
  Command Line: sshd: [net]
    Executable: /usr/sbin/sshd
 Control Group: /system.slice/sshd.service
          Unit: sshd.service
         Slice: system.slice
       Boot ID: 8d2799bb69bc4036b9a98eb197a3da6d
    Machine ID: 9bcaadd8e8ba4302b29cfb084eb68089
      Hostname: localhost.localdomain
       Storage: /var/lib/systemd/coredump/core.sshd.74.8d2799bb69bc4036b9a98eb1>
       Message: Process 10183 (sshd) of user 74 dumped core.
                Stack trace of thread 10183:
                #0  0x00000000b6995370 __GI___select64 ( + 0xda370)
                #1  0x00000000004e96e4 ssh_packet_read_seqnr (sshd + 0x596e4)
                #2  0x00000000004e97fc ssh_dispatch_run_fatal (sshd + 0x597fc)
                #3  0x000000000049dcbc do_ssh2_kex (sshd + 0xdcbc)
                #4  0x000000000049b454 main (sshd + 0xb454)
                #5  0x00000000b68d639c __libc_start_main ( + 0x1b39c)
                #6  0x000000000049baf0 (sshd + 0xbaf0)

Version-Release number of selected component (if applicable):

How reproducible:

Comment 1 Paul Whalen 2020-11-13 20:49:05 UTC
Created attachment 1729215 [details]
sshd backtrace

Comment 2 Jakub Jelen 2020-11-16 09:29:24 UTC
Can you check audit for what syscall was used in your case on ARM which failed? Is it called now select64 or something else?

Comment 3 Paul Whalen 2020-11-17 20:47:39 UTC
type=SECCOMP msg=audit(1605645779.332:638): auid=4294967295 uid=74 gid=74 ses=4294967295 subj=system_u:system_r:sshd_net_t:s0-s0:c0.c1023 pid=796 comm="sshd" exe="/usr/sbin/sshd" sig=31 arch=40000028 syscall=413 compat=0 ip=0xb68db370 code=0x0AUID="unset" UID="sshd" GID="sshd" ARCH=armeb SYSCALL=unknown-syscall(413)

On arm 413 looks to be pselect6_time64

Comment 4 Jakub Jelen 2020-11-18 14:43:47 UTC
Thank you for report and checking the syscall. This is something new. The following patch should address the issue:

diff --git a/sandbox-seccomp-filter.c b/sandbox-seccomp-filter.c
index e0768c06..5065ae7e 100644
--- a/sandbox-seccomp-filter.c
+++ b/sandbox-seccomp-filter.c
@@ -267,6 +267,9 @@ static const struct sock_filter preauth_insns[] = {
 #ifdef __NR_pselect6
+#ifdef __NR_pselect6_time64
+	SC_ALLOW(__NR_pselect6_time64),
 #ifdef __NR_read

I submitted a scratch build with the patch above. Please, check if it will work for you. Then I can fix it in Fedora and report upstream.

Comment 5 Paul Whalen 2020-11-18 15:35:58 UTC
(In reply to Jakub Jelen from comment #4)

> I submitted a scratch build with the patch above. Please, check if it will
> work for you. Then I can fix it in Fedora and report upstream.

Thanks! That works as expected.

Comment 6 Fedora Update System 2020-11-19 14:47:07 UTC
FEDORA-2020-413ab3bca3 has been submitted as an update to Fedora 33.

Comment 7 Fedora Update System 2020-11-20 02:15:00 UTC
FEDORA-2020-413ab3bca3 has been pushed to the Fedora 33 testing repository.
In short time you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --advisory=FEDORA-2020-413ab3bca3`
You can provide feedback for this update here:

See also for more information on how to test updates.

Comment 8 Fedora Update System 2020-11-27 01:22:51 UTC
FEDORA-2020-413ab3bca3 has been pushed to the Fedora 33 stable repository.
If problem still persists, please make note of it in this bug report.

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