krshd hangs in linux nightly testing

A typical stack trace:

#0  0xffffe002 in ?? ()
#1  0x420da75f in syslog () from /lib/tls/libc.so.6
#2  0x0804ad06 in cleanup (signumber=15) at krshd.c:567
#3  <signal handler called>
#4  0xffffe000 in ?? ()
#5  0x4202774e in sigaction () from /lib/tls/libc.so.6
#6  0x0804ac82 in cleanup (signumber=1) at krshd.c:548
#7  <signal handler called>
#8  0xffffe002 in ?? ()
#9  0x4202774e in sigaction () from /lib/tls/libc.so.6
#10 0x420daa21 in vsyslog () from /lib/tls/libc.so.6
#11 0x420da75f in syslog () from /lib/tls/libc.so.6
#12 0x0804b670 in doit (f=3, fromp=0xbfffda50) at krshd.c:1313
#13 0x0804ab87 in main (argc=11, argv=0xbfffdb34) at krshd.c:459
#14 0x420156a4 in __libc_start_main () from /lib/tls/libc.so.6

Yes, we're calling syslog from inside a signal handler.  Yes, this is
bad.  And from some poking about that I did earlier, it appears that
there's some locking code in vsyslog which may be deadlocking in the
nested call.  And this usually seems to happen when logging the "shell
process completed" message.

This is a quick patch to switch off the signal handlers before logging
that message.  I suspect the breakage happens earlier, though, so this
might not fix the bug, just maybe move it around a little.

* krshd.c (ignore_signals): Split out from cleanup().
(doit): Call it when the shell process has completed, before calling syslog.

ticket: new
status: open

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@15800 dc483132-0cff-0310-8789-dd5450dbe970

diff --git a/src/appl/bsd/ChangeLog b/src/appl/bsd/ChangeLog
index 3a096e10771b71e2e85799b176ac82308e27f509..75066eedb4f071c636400cdf51179be372d88f48 100644 (file)
--- a/src/appl/bsd/ChangeLog
+++ b/src/appl/bsd/ChangeLog
@@ -1,3 +1,9 @@
+2003-08-29  Ken Raeburn  <raeburn@mit.edu>
+
+       * krshd.c (ignore_signals): Split out from cleanup().
+       (doit): Call it when the shell process has completed, before
+       calling syslog.
+
 2003-05-23  Ken Raeburn  <raeburn@mit.edu>
 
        * configure.in: Don't use libkrb524.a any more.

diff --git a/src/appl/bsd/krshd.c b/src/appl/bsd/krshd.c
index d625d8bd97707daa437bb8e9acb616e89670fb47..9fde43d6eddea24b48428c5f4abb5ec9a1ee51d9 100644 (file)
--- a/src/appl/bsd/krshd.c
+++ b/src/appl/bsd/krshd.c
@@ -535,9 +535,8 @@ int auth_sys = 0;   /* Which version of Kerberos used to authenticate */
 #define KRB5_RECVAUTH_V4       4
 #define KRB5_RECVAUTH_V5       5
 
-static krb5_sigtype
-cleanup(signumber)
-     int signumber;
+static void
+ignore_signals()
 {
 #ifdef POSIX_SIGNALS
     struct sigaction sa;
@@ -561,6 +560,13 @@ cleanup(signumber)
     
     killpg(pid, SIGTERM);
 #endif
+}
+
+static krb5_sigtype
+cleanup(signumber)
+     int signumber;
+{
+    ignore_signals();
     wait(0);
     
     pty_logwtmp(ttyn,"","");
@@ -1302,13 +1308,14 @@ void doit(f, fromp)
                        } else if (wcc != cc) {
                          syslog(LOG_INFO, "only wrote %d/%d to child", 
                                 wcc, cc);
-               }
-               }
+                       }
+                   }
                }
            } while ((port&&FD_ISSET(s, &readfrom)) ||
                     FD_ISSET(f, &readfrom) ||
                     (port&&FD_ISSET(pv[0], &readfrom) )||
                     FD_ISSET(pw[0], &readfrom));
+           ignore_signals();
 #ifdef KERBEROS
            syslog(LOG_INFO ,
                   "Shell process completed.");