From: Haavard Skinnemoen Date: Wed, 27 Feb 2008 13:04:29 +0000 (+0100) Subject: avr32: Fix OCD refcounting bug X-Git-Tag: v2.6.25-rc4~143^2 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=325d6f5593b40b5a48cf4ade74c01681f2ff6044;p=linux-2.6 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 --- diff --git a/arch/avr32/kernel/process.c b/arch/avr32/kernel/process.c index faf8d0e768..7f4af0b1e1 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);