4.4-stable review patch. If anyone has any objections, please let me know.
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From: Vegard Nossum vegard.nossum@oracle.com
commit b0f5a8f32e8bbdaae1abb8abe2d3cbafaba57e08 upstream.
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 linux@roeck-us.net Tested-by: Guenter Roeck linux@roeck-us.net # MIPS only Acked-by: Stafford Horne shorne@gmail.com Acked-by: Oleg Nesterov oleg@redhat.com Cc: Ralf Baechle ralf@linux-mips.org Cc: linux-mips@linux-mips.org Cc: Jonas Bonn jonas@southpole.se Cc: Stefan Kristiansson stefan.kristiansson@saunalahti.fi Cc: openrisc@lists.librecores.org Cc: Jamie Iles jamie.iles@oracle.com Cc: Thomas Gleixner tglx@linutronix.de Signed-off-by: Vegard Nossum vegard.nossum@oracle.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Amit Pundir amit.pundir@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/mips/kernel/process.c | 1 - arch/openrisc/kernel/process.c | 2 -- 2 files changed, 3 deletions(-)
--- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -115,7 +115,6 @@ int copy_thread(unsigned long clone_flag 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;
--- a/arch/openrisc/kernel/process.c +++ b/arch/openrisc/kernel/process.c @@ -152,8 +152,6 @@ copy_thread(unsigned long clone_flags, u
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);