vsnprintf crashes (Segmentation fault) from /lib64/tls/libc.so.6
 

In one 64 bit linux 5 box vsnprintf is crashing.
It is not consistent but after some iteration it crashes
with same input.

following is the stack trace:-

--------------------------------------------------------
#0 0x0000003707e796d0 in strlen () from /lib64/libc.so.6
(gdb) bt
#0 0x0000003707e796d0 in strlen () from /lib64/libc.so.6
#1 0x00002b9e349764d7 in dosprintf () from /opt/SUNWwebserver/lib/libnspr4.so
#2 0x00002b9e34976974 in PR_vsnprintf () from /opt/SUNWwebserver/lib/libnspr4.so
.......
------------------------------------------------------------

code snippet is as below:-

............
// msg has been successfully allocated
// PR_vsnprintf is a simple wrapper on vsprintf
va_list args;
va_start(args, fmt);
PR_vsnprintf(msg, MAX_MSG_LEN, fmt, args);
va_end(args);

------------------------------------------------------------

system configuration is:-

cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.4 (Tikanga)

Any idea on this issue?