From 325d6f5593b40b5a48cf4ade74c01681f2ff6044 Mon Sep 17 00:00:00 2001 From: Haavard Skinnemoen Date: Wed, 27 Feb 2008 14:04:29 +0100 Subject: [PATCH] avr32: Fix OCD refcounting bug Iff the parent has TIF_DEBUG set, _and_ clone_flags includes CLONE_PTRACE we should set the TIF_DEBUG flag for the child and increment the ocd refcount. Otherwise, the TIF_DEBUG flag must be unset. Currently, the child inherits TIF_DEBUG from the parent before copy_thread is called, so TIF_DEBUG may be already be set before we determine whether the child is supposed to inherit debugging capabilities from the parent or not. This means that ocd_enable() won't increment the refcount, because TIF_DEBUG is already set, and that TIF_DEBUG will be set for processes that aren't being debugged. This leads to a refcounting asymmetry, which may show up as ------------[ cut here ]------------ Badness at arch/avr32/kernel/ocd.c:73 PC is at ocd_disable+0x34/0x60 LR is at put_lock_stats+0xa/0x20 as reported by David Brownell. Happens when strace'ing a process that forks a new child process, e.g. "strace mount -tjffs2 mtd1 /mnt", and subsequently killing the child process (e.g. "umount /mnt".) Signed-off-by: Haavard Skinnemoen --- arch/avr32/kernel/process.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/avr32/kernel/process.c b/arch/avr32/kernel/process.c index faf8d0e76801..7f4af0b1e111 100644 --- a/arch/avr32/kernel/process.c +++ b/arch/avr32/kernel/process.c @@ -348,6 +348,7 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long usp, p->thread.cpu_context.ksp = (unsigned long)childregs; p->thread.cpu_context.pc = (unsigned long)ret_from_fork; + clear_tsk_thread_flag(p, TIF_DEBUG); if ((clone_flags & CLONE_PTRACE) && test_thread_flag(TIF_DEBUG)) ocd_enable(p); -- 2.20.1