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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id x22-20020a170902821600b00189ac5a2340sm5754875pln.124.2022.12.02.14.58.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Dec 2022 14:58:14 -0800 (PST) Date: Fri, 2 Dec 2022 14:58:13 -0800 From: Kees Cook To: jeffxu@chromium.org Cc: skhan@linuxfoundation.org, akpm@linux-foundation.org, dmitry.torokhov@gmail.com, dverkamp@chromium.org, hughd@google.com, jeffxu@google.com, jorgelo@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, mnissler@chromium.org, jannh@google.com, linux-hardening@vger.kernel.org Subject: Re: [PATCH v3] mm/memfd: security hook for memfd_create Message-ID: <202212021457.EC46B27677@keescook> References: <20221202013404.163143-1-jeffxu@google.com> <20221202013404.163143-6-jeffxu@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221202013404.163143-6-jeffxu@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 02, 2022 at 01:34:03AM +0000, jeffxu@chromium.org wrote: > From: Jeff Xu > > The new security_memfd_create allows lsm to check flags of > memfd_create. > > The security by default system (such as chromeos) can use this > to implement system wide lsm to allow only non-executable memfd > being created. > > Signed-off-by: Jeff Xu > --- > include/linux/lsm_hook_defs.h | 1 + > include/linux/lsm_hooks.h | 4 ++++ > include/linux/security.h | 6 ++++++ > mm/memfd.c | 5 +++++ > 4 files changed, 16 insertions(+) > > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h > index ec119da1d89b..fd40840927c8 100644 > --- a/include/linux/lsm_hook_defs.h > +++ b/include/linux/lsm_hook_defs.h > @@ -164,6 +164,7 @@ LSM_HOOK(int, 0, file_alloc_security, struct file *file) > LSM_HOOK(void, LSM_RET_VOID, file_free_security, struct file *file) > LSM_HOOK(int, 0, file_ioctl, struct file *file, unsigned int cmd, > unsigned long arg) > +LSM_HOOK(int, 0, memfd_create, char *name, unsigned int flags) > LSM_HOOK(int, 0, mmap_addr, unsigned long addr) > LSM_HOOK(int, 0, mmap_file, struct file *file, unsigned long reqprot, > unsigned long prot, unsigned long flags) > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > index 4ec80b96c22e..5a18a6552278 100644 > --- a/include/linux/lsm_hooks.h > +++ b/include/linux/lsm_hooks.h > @@ -543,6 +543,10 @@ > * simple integer value. When @arg represents a user space pointer, it > * should never be used by the security module. > * Return 0 if permission is granted. > + * @memfd_create: > + * @name is the name of memfd file. > + * @flags is the flags used in memfd_create. > + * Return 0 if permission is granted. > * @mmap_addr : > * Check permissions for a mmap operation at @addr. > * @addr contains virtual address that will be used for the operation. > diff --git a/include/linux/security.h b/include/linux/security.h > index ca1b7109c0db..5b87a780822a 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -384,6 +384,7 @@ int security_file_permission(struct file *file, int mask); > int security_file_alloc(struct file *file); > void security_file_free(struct file *file); > int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg); > +int security_memfd_create(char *name, unsigned int flags); > int security_mmap_file(struct file *file, unsigned long prot, > unsigned long flags); > int security_mmap_addr(unsigned long addr); > @@ -963,6 +964,11 @@ static inline int security_file_ioctl(struct file *file, unsigned int cmd, > return 0; > } > > +static inline int security_memfd_create(char *name, unsigned int flags) > +{ > + return 0; > +} I think this is missing the security/security.c changes for the non-inline version? -Kees > + > static inline int security_mmap_file(struct file *file, unsigned long prot, > unsigned long flags) > { > diff --git a/mm/memfd.c b/mm/memfd.c > index 69e897dea6d5..96dcfbfed09e 100644 > --- a/mm/memfd.c > +++ b/mm/memfd.c > @@ -346,6 +346,11 @@ SYSCALL_DEFINE2(memfd_create, > goto err_name; > } > > + /* security hook for memfd_create */ > + error = security_memfd_create(name, flags); > + if (error) > + return error; > + > if (flags & MFD_HUGETLB) { > file = hugetlb_file_setup(name, 0, VM_NORESERVE, > HUGETLB_ANONHUGE_INODE, > -- > 2.39.0.rc0.267.gcb52ba06e7-goog > -- Kees Cook