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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id m28sm335674pgl.9.2021.09.03.14.47.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Sep 2021 14:47:02 -0700 (PDT) Date: Fri, 3 Sep 2021 14:47:01 -0700 From: Kees Cook To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, ccross@google.com, sumit.semwal@linaro.org, mhocko@suse.com, dave.hansen@intel.com, willy@infradead.org, kirill.shutemov@linux.intel.com, vbabka@suse.cz, hannes@cmpxchg.org, corbet@lwn.net, viro@zeniv.linux.org.uk, rdunlap@infradead.org, kaleshsingh@google.com, peterx@redhat.com, rppt@kernel.org, peterz@infradead.org, catalin.marinas@arm.com, vincenzo.frascino@arm.com, chinwen.chang@mediatek.com, axelrasmussen@google.com, aarcange@redhat.com, jannh@google.com, apopple@nvidia.com, jhubbard@nvidia.com, yuzhao@google.com, will@kernel.org, fenghua.yu@intel.com, thunder.leizhen@huawei.com, hughd@google.com, feng.tang@intel.com, jgg@ziepe.ca, guro@fb.com, tglx@linutronix.de, krisman@collabora.com, chris.hyser@oracle.com, pcc@google.com, ebiederm@xmission.com, axboe@kernel.dk, legion@kernel.org, eb@emlix.com, gorcunov@gmail.com, songmuchun@bytedance.com, viresh.kumar@linaro.org, thomascedeno@google.com, sashal@kernel.org, cxfcosmos@gmail.com, linux@rasmusvillemoes.dk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, kernel-team@android.com Subject: Re: [PATCH v9 2/3] mm: add a field to store names for private anonymous memory Message-ID: <202109031439.B58932AF0@keescook> References: <20210902231813.3597709-1-surenb@google.com> <20210902231813.3597709-2-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210902231813.3597709-2-surenb@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (Sorry, a few more things jumped out at me when I looked again...) On Thu, Sep 02, 2021 at 04:18:12PM -0700, Suren Baghdasaryan wrote: > [...] > diff --git a/kernel/sys.c b/kernel/sys.c > index 72c7639e3c98..25118902a376 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -2299,6 +2299,64 @@ int __weak arch_prctl_spec_ctrl_set(struct task_struct *t, unsigned long which, > > #define PR_IO_FLUSHER (PF_MEMALLOC_NOIO | PF_LOCAL_THROTTLE) > > +#ifdef CONFIG_MMU > + > +#define ANON_VMA_NAME_MAX_LEN 256 > + > +static inline bool is_valid_name_char(char ch) > +{ > + /* printable ascii characters, except [ \ ] */ > + return (ch > 0x1f && ch < 0x5b) || (ch > 0x5d && ch < 0x7f); > +} In the back of my mind, I feel like disallowing backtick would be nice, but then if $, (, and ) are allowed, it doesn't matter, and that seems too limiting. :) > + > +static int prctl_set_vma(unsigned long opt, unsigned long addr, > + unsigned long size, unsigned long arg) > +{ > + struct mm_struct *mm = current->mm; > + const char __user *uname; > + char *name, *pch; > + int error; > + > + switch (opt) { > + case PR_SET_VMA_ANON_NAME: > + uname = (const char __user *)arg; > + if (!uname) { > + /* Reset the name */ > + name = NULL; > + goto set_name; > + } > + > + name = strndup_user(uname, ANON_VMA_NAME_MAX_LEN); > + > + if (IS_ERR(name)) > + return PTR_ERR(name); > + > + for (pch = name; *pch != '\0'; pch++) { > + if (!is_valid_name_char(*pch)) { > + kfree(name); > + return -EINVAL; > + } > + } > +set_name: > + mmap_write_lock(mm); > + error = madvise_set_anon_name(mm, addr, size, name); > + mmap_write_unlock(mm); > + kfree(name); > + break; This is a weird construct with a needless goto. Why not: switch (opt) { case PR_SET_VMA_ANON_NAME: uname = (const char __user *)arg; if (uname) { name = strndup_user(uname, ANON_VMA_NAME_MAX_LEN); if (IS_ERR(name)) return PTR_ERR(name); for (pch = name; *pch != '\0'; pch++) { if (!is_valid_name_char(*pch)) { kfree(name); return -EINVAL; } } } else { /* Reset the name */ name = NULL; } mmap_write_lock(mm); error = madvise_set_anon_name(mm, addr, size, name); mmap_write_unlock(mm); kfree(name); break; -- Kees Cook