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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id q15-20020a17090a2dcf00b001faafa42a9esm1086148pjm.26.2022.09.16.02.46.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Sep 2022 02:46:42 -0700 (PDT) Date: Fri, 16 Sep 2022 02:46:39 -0700 From: Kees Cook To: Matthew Wilcox Cc: Yu Zhao , Andrew Morton , dev@der-flo.net, Linux-MM , Uladzislau Rezki , bugzilla-daemon@kernel.org Subject: Re: [Bug 216489] New: Machine freezes due to memory lock Message-ID: <202209160230.CE9E0E51@keescook> References: <20220915133931.ee0a6c8a86c59a144828eb60@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663321605; a=rsa-sha256; cv=none; b=bHy/DWJZtGKoxvm7A6Ipg9Z3fd40gAzT9/n80KvdzvZ2PGPk14vTiu60Ac5MhyiQoNUQqa pASZxZ6fk8l4MOUwkYIYHmn1LCIre5IPxFn1Uah3LADBA8o8FJJ9uXDQ9kiSVmyBqqdk/6 OmTHXNQ3E50KFlOKIWs2lPQwFs6cq8o= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=ioRo1FPT; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf07.hostedemail.com: domain of keescook@chromium.org designates 209.85.215.180 as permitted sender) smtp.mailfrom=keescook@chromium.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663321605; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Nz4xHlonAZGpWjIjVTDhSZxWqGe/LbrSjZD6Lj4tLE8=; b=pJSWJ+Hm58xbb93VLi3RHA1nlj4w31FD4RCzvF6LN3HEl+/AzDFiQI5hdzl9qIAT1t8sA5 9BsCjC9Dz9+E3Qysy2wnhjF40UsOUyryLXX41T+keZJ1lY937h290ffJ6kpYyBM7Vhg5f/ nkTLw4HcpMbnT+Eq+RErBAKWHwlPxTI= X-Stat-Signature: 4u8qd4ymk5iy1knr7ncfwftcc7dmwsag X-Rspamd-Queue-Id: 8CEEA40094 Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=ioRo1FPT; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf07.hostedemail.com: domain of keescook@chromium.org designates 209.85.215.180 as permitted sender) smtp.mailfrom=keescook@chromium.org X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1663321605-529948 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Sep 16, 2022 at 09:38:33AM +0100, Matthew Wilcox wrote: > On Thu, Sep 15, 2022 at 05:59:56PM -0600, Yu Zhao wrote: > > I think this is a manifest of the lockdep warning I reported a couple > > of weeks ago: > > https://lore.kernel.org/r/CAOUHufaPshtKrTWOz7T7QFYUNVGFm0JBjvM700Nhf9qEL9b3EQ@mail.gmail.com/ > > That would certainly match the symptoms. > > Turning vmap_lock into an NMI-safe lock would be bad. I don't even know > if we have primitives for that (it's not like you can disable an NMI > ...) > > I don't quite have time to write a patch right now. Perhaps something > like: > > struct vmap_area *find_vmap_area_nmi(unsigned long addr) > { > struct vmap_area *va; > > if (spin_trylock(&vmap_area_lock)) > return NULL; > va = __find_vmap_area(addr, &vmap_area_root); > spin_unlock(&vmap_area_lock); > > return va; > } > > and then call find_vmap_area_nmi() in check_heap_object(). I may have > the polarity of the return value of spin_trylock() incorrect. I think we'll need something slightly tweaked, since this would return NULL under any contention (and a NULL return is fatal in check_heap_object()). It seems like we need to explicitly check for being in nmi context in check_heap_object() to deal with it? Like this (only build tested): diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index 096d48aa3437..c8a00f181a11 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -216,6 +216,7 @@ void free_vm_area(struct vm_struct *area); extern struct vm_struct *remove_vm_area(const void *addr); extern struct vm_struct *find_vm_area(const void *addr); struct vmap_area *find_vmap_area(unsigned long addr); +struct vmap_area *find_vmap_area_try(unsigned long addr); static inline bool is_vm_area_hugepages(const void *addr) { diff --git a/mm/usercopy.c b/mm/usercopy.c index c1ee15a98633..9f943c29e7ec 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -173,7 +173,16 @@ static inline void check_heap_object(const void *ptr, unsigned long n, } if (is_vmalloc_addr(ptr)) { - struct vmap_area *area = find_vmap_area(addr); + struct vmap_area *area; + + if (!in_nmi()) { + area = find_vmap_area(addr); + } else { + area = find_vmap_area_try(addr); + /* Give up under NMI to avoid deadlocks. */ + if (!area) + return; + } if (!area) usercopy_abort("vmalloc", "no area", to_user, 0, n); diff --git a/mm/vmalloc.c b/mm/vmalloc.c index dd6cdb201195..f14f1902c2f6 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1840,6 +1840,17 @@ struct vmap_area *find_vmap_area(unsigned long addr) return va; } +struct vmap_area *find_vmap_area_try(unsigned long addr) +{ + struct vmap_area *va = NULL; + + if (spin_trylock(&vmap_area_lock)) { + va = __find_vmap_area(addr, &vmap_area_root); + spin_unlock(&vmap_area_lock); + } + return va; +} + /*** Per cpu kva allocator ***/ /* -- Kees Cook