From b0f5a8f32e8bbdaae1abb8abe2d3cbafaba57e08 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Mon, 29 May 2017 09:22:07 +0200 Subject: [PATCH] kthread: fix boot hang (regression) on MIPS/OpenRISC This fixes a regression in commit 4d6501dce079 where I didn't notice that MIPS and OpenRISC were reinitialising p->{set,clear}_child_tid to NULL after our initialisation in copy_process(). We can simply get rid of the arch-specific initialisation here since it is now always done in copy_process() before hitting copy_thread{,_tls}(). Review notes: - As far as I can tell, copy_process() is the only user of copy_thread_tls(), which is the only caller of copy_thread() for architectures that don't implement copy_thread_tls(). - After this patch, there is no arch-specific code touching p->set_child_tid or p->clear_child_tid whatsoever. - It may look like MIPS/OpenRISC wanted to always have these fields be NULL, but that's not true, as copy_process() would unconditionally set them again _after_ calling copy_thread_tls() before commit 4d6501dce079. Fixes: 4d6501dce079c1eb6bf0b1d8f528a5e81770109e ("kthread: Fix use-after-free if kthread fork fails") Reported-by: Guenter Roeck Tested-by: Guenter Roeck # MIPS only Acked-by: Stafford Horne Acked-by: Oleg Nesterov Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: Jonas Bonn Cc: Stefan Kristiansson Cc: openrisc@lists.librecores.org Cc: Jamie Iles Cc: Thomas Gleixner Signed-off-by: Vegard Nossum Signed-off-by: Linus Torvalds --- arch/mips/kernel/process.c | 1 - arch/openrisc/kernel/process.c | 2 -- 2 files changed, 3 deletions(-) diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index 918d4c73e951..5351e1f3950d 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -120,7 +120,6 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long usp, struct thread_info *ti = task_thread_info(p); struct pt_regs *childregs, *regs = current_pt_regs(); unsigned long childksp; - p->set_child_tid = p->clear_child_tid = NULL; childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32; diff --git a/arch/openrisc/kernel/process.c b/arch/openrisc/kernel/process.c index f8da545854f9..106859ae27ff 100644 --- a/arch/openrisc/kernel/process.c +++ b/arch/openrisc/kernel/process.c @@ -167,8 +167,6 @@ copy_thread(unsigned long clone_flags, unsigned long usp, top_of_kernel_stack = sp; - p->set_child_tid = p->clear_child_tid = NULL; - /* Locate userspace context on stack... */ sp -= STACK_FRAME_OVERHEAD; /* redzone */ sp -= sizeof(struct pt_regs); -- 2.20.1