Didn't see  a fix for this so here it is. Tried using "ltrace -i" on a 
64 bit executable when ltrace was a 32 bit executable. The kernel threw 
an oops.

The find_target routine (arch/x86/ia32/ptrace32.c) doesn't deal with a 
NULL return from  find_task_by_pid properly - if NULL is returned 
put_task_struct() is still called.

mark