On 04/04/2018 23:53, David Rientjes wrote: > On Wed, 4 Apr 2018, Laurent Dufour wrote: > >>> I also think the following is needed: >>> >>> diff --git a/fs/exec.c b/fs/exec.c >>> --- a/fs/exec.c >>> +++ b/fs/exec.c >>> @@ -312,6 +312,10 @@ static int __bprm_mm_init(struct linux_binprm *bprm) >>> vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; >>> vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); >>> INIT_LIST_HEAD(&vma->anon_vma_chain); >>> +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT >>> + seqcount_init(&vma->vm_sequence); >>> + atomic_set(&vma->vm_ref_count, 0); >>> +#endif >>> >>> err = insert_vm_struct(mm, vma); >>> if (err) >> >> No, this not needed because the vma is allocated with kmem_cache_zalloc() so >> vm_ref_count is 0, and insert_vm_struc() will later call >> __vma_link_rb() which will call seqcount_init(). >> >> Furhtermore, in case of error, the vma structure is freed without calling >> get_vma() so there is risk of lockdep warning. >> > > Perhaps you're working from a different tree than I am, or you fixed the > lockdep warning differently when adding to dup_mmap() and mmap_region(). > > I got the following two lockdep errors. > > I fixed it locally by doing the seqcount_init() and atomic_set() > everywhere a vma could be initialized. That's weird, I don't get that on my side with lockdep activated. There is a call to seqcount_init() in dup_mmap(), in mmap_region() and __vma_link_rb() and that's enough to cover all the case. That's being said, it'll be better call seqcount_init each time as soon as a vma structure is allocated. For the vm_ref_count value, as most of the time the vma is zero allocated, I don't think this is needed. I just have to check when new_vma = *old_vma is done, but this often just follow a vma allocation. > > INFO: trying to register non-static key. > the code is fine but needs lockdep annotation. > turning off the locking correctness validator. > CPU: 12 PID: 1 Comm: init Not tainted > Call Trace: > [<ffffffff8b12026f>] dump_stack+0x67/0x98 > [<ffffffff8a92b616>] register_lock_class+0x1e6/0x4e0 > [<ffffffff8a92cfe9>] __lock_acquire+0xb9/0x1710 > [<ffffffff8a92ef3a>] lock_acquire+0xba/0x200 > [<ffffffff8aa827df>] mprotect_fixup+0x10f/0x310 > [<ffffffff8aade3fd>] setup_arg_pages+0x12d/0x230 > [<ffffffff8ab4564a>] load_elf_binary+0x44a/0x1740 > [<ffffffff8aadde9b>] search_binary_handler+0x9b/0x1e0 > [<ffffffff8ab44e96>] load_script+0x206/0x270 > [<ffffffff8aadde9b>] search_binary_handler+0x9b/0x1e0 > [<ffffffff8aae0355>] do_execveat_common.isra.32+0x6b5/0x9d0 > [<ffffffff8aae069c>] do_execve+0x2c/0x30 > [<ffffffff8a80047b>] run_init_process+0x2b/0x30 > [<ffffffff8b1358d4>] kernel_init+0x54/0x110 > [<ffffffff8b2001ca>] ret_from_fork+0x3a/0x50 > > and > > INFO: trying to register non-static key. > the code is fine but needs lockdep annotation. > turning off the locking correctness validator. > CPU: 21 PID: 1926 Comm: mkdir Not tainted > Call Trace: > [<ffffffff985202af>] dump_stack+0x67/0x98 > [<ffffffff97d2b616>] register_lock_class+0x1e6/0x4e0 > [<ffffffff97d2cfe9>] __lock_acquire+0xb9/0x1710 > [<ffffffff97d2ef3a>] lock_acquire+0xba/0x200 > [<ffffffff97e73c09>] unmap_page_range+0x89/0xaa0 > [<ffffffff97e746af>] unmap_single_vma+0x8f/0x100 > [<ffffffff97e74a1b>] unmap_vmas+0x4b/0x90 > [<ffffffff97e7f833>] exit_mmap+0xa3/0x1c0 > [<ffffffff97cc1b23>] mmput+0x73/0x120 > [<ffffffff97ccbacd>] do_exit+0x2bd/0xd60 > [<ffffffff97ccc5b7>] SyS_exit+0x17/0x20 > [<ffffffff97c01f1d>] do_syscall_64+0x6d/0x1a0 > [<ffffffff9860005a>] entry_SYSCALL_64_after_hwframe+0x26/0x9b > > I think it would just be better to generalize vma allocation to initialize > certain fields and init both spf fields properly for > CONFIG_SPECULATIVE_PAGE_FAULT. It's obviously too delicate as is. >
