From: Jeff Dike A bit of defensive programming - during development, it ocassionally happens that a call to init_new_context is missed, resulting in context holding a host pid of zero. When that address space is torn down, destroy_context does a kill(0), which instantly kills the whole UML without any errors whatsoever. This patch add a check for pids less than 2, to also catch 1 and negative pids. Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton --- arch/um/kernel/skas/mmu.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff -puN arch/um/kernel/skas/mmu.c~uml-dont-kill-pid-0 arch/um/kernel/skas/mmu.c --- a/arch/um/kernel/skas/mmu.c~uml-dont-kill-pid-0 +++ a/arch/um/kernel/skas/mmu.c @@ -164,8 +164,20 @@ void destroy_context(struct mm_struct *m if (proc_mm) os_close_file(mmu->id.u.mm_fd); - else + else { + /* + * If init_new_context wasn't called, this will be + * zero, resulting in a kill(0), which will result in the + * whole UML suddenly dying. Also, cover negative and + * 1 cases, since they shouldn't happen either. + */ + if (mmu->id.u.pid < 2) { + printk(KERN_ERR "corrupt mm_context - pid = %d\n", + mmu->id.u.pid); + return; + } os_kill_ptraced_process(mmu->id.u.pid, 1); + } if (skas_needs_stub) free_page(mmu->id.stack); _