[Bug 349919] [NEW] ssh client sometimes hangs

[Tony Luck]

Public bug reported:

$ lsb_release -rd
Description:	Ubuntu 8.10
Release:	8.10
$ apt-cache policy openssh-client
openssh-client:
  Installed: 1:5.1p1-3ubuntu1
  Candidate: 1:5.1p1-3ubuntu1
  Version table:
 *** 1:5.1p1-3ubuntu1 0
        500 http://us.archive.ubuntu.com intrepid/main Packages
        100 /var/lib/dpkg/status

I have .ssh key files that I generated years ago.  I copied them to
~/.ssh on my ubuntu system. Most of the time when I use ssh to run a
command on another system it works fine.  Once in 50 times ssh hangs
locally.

This is not a network problem ... same issue happens with "localhost".
E.g. if I run:

$ while :
> do ssh localhost date
> done

It will print the date a few dozen times, then the loop hangs (^C
interrupts it).

I tried using strace to see what was happening.  The ssh process was hung reading from a socket.
Looking back through the strace, the socket was connected to some local keyring thing.
Here are some relevent lines from strace output:

socket(PF_FILE, SOCK_STREAM, 0)         = 4
fcntl(4, F_SETFD, FD_CLOEXEC)           = 0
connect(4, {sa_family=AF_FILE, path="/tmp/keyring-fed2nU/ssh"}, 110) = 0
write(4, "\0\0\0\1", 4)                 = 4
write(4, "\v", 1)                       = 1
read(4, "\0\0\2h", 4)                   = 4
read(4, "\f\0\0\0\2\0\0\0\225\0\0\0\7ssh-rsa\0\0\0\1#\0\0\0\201"..., 616) = 616
write(3, "$K \250\310\200\247\266-\25\257\212f\226h\234\f\275a\310"..., 64) = 64
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\34t\351\267\262/\362\315\33\r\3019\301\361dX\264\276\377"..., 8192) = 80
futex(0x7f956651f2e0, 0x81 /* FUTEX_??? */, 2147483647) = 0
futex(0x7f956651f160, 0x81 /* FUTEX_??? */, 2147483647) = 0
futex(0x7f9567385450, 0x81 /* FUTEX_??? */, 2147483647) = 0
futex(0x7f9567159590, 0x81 /* FUTEX_??? */, 2147483647) = 0
futex(0x7f95671599d0, 0x81 /* FUTEX_??? */, 2147483647) = 0

....

open("/dev/urandom", O_RDONLY)          = 5
fstat(5, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 9), ...}) = 0
read(5, "\21\207y;\216\357\361\37\310\230\300\211GYpr\236a\235\t"..., 20) = 20
close(5)                                = 0
write(3, "\314\331H\3711\274\25\v@\201\201vG\rO\230\273d\277&8X2"..., 240) = 240
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\234?r\352\30(\373T\277!bm\224W\30P\247\270\313\234\341"..., 8192) = 192
brk(0x7f95690d9000)                     = 0x7f95690d9000
brk(0x7f95690d8000)                     = 0x7f95690d8000
write(4, "\0\0\1\207", 4)               = 4
write(4, "\r\0\0\0\225\0\0\0\7ssh-rsa\0\0\0\1#\0\0\0\201\0\300\r"..., 391) = 391
read(4, 0x7fff703fa880, 4)              = ? ERESTARTSYS (To be restarted)
--- SIGINT (Interrupt) @ 0 (0) ---
+++ killed by SIGINT +++

** Affects: openssh (Ubuntu)
     Importance: Undecided
         Status: New

-- 
ssh client sometimes hangs
https://bugs.launchpad.net/bugs/349919
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