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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id 12sm6465419pfi.60.2019.06.22.15.54.45 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sat, 22 Jun 2019 15:54:45 -0700 (PDT) Date: Sat, 22 Jun 2019 15:54:44 -0700 From: Kees Cook To: Casey Schaufler Cc: casey.schaufler@intel.com, jmorris@namei.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, john.johansen@canonical.com, penguin-kernel@i-love.sakura.ne.jp, paul@paul-moore.com, sds@tycho.nsa.gov Subject: Re: [PATCH v3 18/24] LSM: Use lsmcontext in security_dentry_init_security Message-ID: <201906221554.8AABDE034@keescook> References: <20190621185233.6766-1-casey@schaufler-ca.com> <20190621185233.6766-19-casey@schaufler-ca.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190621185233.6766-19-casey@schaufler-ca.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Jun 21, 2019 at 11:52:27AM -0700, Casey Schaufler wrote: > Change the security_dentry_init_security() interface to > fill an lsmcontext structure instead of a void * data area > and a length. The lone caller of this interface is NFS4, > which may make copies of the data using its own mechanisms. > A rework of the nfs4 code to use the lsmcontext properly > is a significant project, so the coward's way out is taken, > and the lsmcontext data from security_dentry_init_security() > is copied, then released directly. > > Signed-off-by: Casey Schaufler > --- > fs/nfs/nfs4proc.c | 26 ++++++++++++++++---------- > include/linux/security.h | 7 +++---- > security/security.c | 20 ++++++++++++++++---- > 3 files changed, 35 insertions(+), 18 deletions(-) > > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c > index af1c0db29c39..952f805965bb 100644 > --- a/fs/nfs/nfs4proc.c > +++ b/fs/nfs/nfs4proc.c > @@ -113,6 +113,7 @@ static inline struct nfs4_label * > nfs4_label_init_security(struct inode *dir, struct dentry *dentry, > struct iattr *sattr, struct nfs4_label *label) > { > + struct lsmcontext context; > int err; > > if (label == NULL) > @@ -122,21 +123,26 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry, > return NULL; > > err = security_dentry_init_security(dentry, sattr->ia_mode, > - &dentry->d_name, (void **)&label->label, &label->len); > - if (err == 0) > - return label; > + &dentry->d_name, &context); > + > + if (err) > + return NULL; > + > + label->label = kmemdup(context.context, context.len, GFP_KERNEL); > + if (label->label == NULL) > + label = NULL; > + else > + label->len = context.len; > + > + security_release_secctx(&context); > + > + return label; > > - return NULL; > } > static inline void > nfs4_label_release_security(struct nfs4_label *label) > { > - struct lsmcontext scaff; /* scaffolding */ > - > - if (label) { > - lsmcontext_init(&scaff, label->label, label->len, 0); > - security_release_secctx(&scaff); > - } > + kfree(label->label); > } > static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label) > { > diff --git a/include/linux/security.h b/include/linux/security.h > index 3cbe43db16f5..2a2785a4e752 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -348,8 +348,8 @@ int security_sb_clone_mnt_opts(const struct super_block *oldsb, > int security_add_mnt_opt(const char *option, const char *val, > int len, void **mnt_opts); > int security_dentry_init_security(struct dentry *dentry, int mode, > - const struct qstr *name, void **ctx, > - u32 *ctxlen); > + const struct qstr *name, > + struct lsmcontext *ctx); > int security_dentry_create_files_as(struct dentry *dentry, int mode, > struct qstr *name, > const struct cred *old, > @@ -720,8 +720,7 @@ static inline void security_inode_free(struct inode *inode) > static inline int security_dentry_init_security(struct dentry *dentry, > int mode, > const struct qstr *name, > - void **ctx, > - u32 *ctxlen) > + struct lsmcontext *ctx) > { > return -EOPNOTSUPP; > } > diff --git a/security/security.c b/security/security.c > index f461ab3fb9c4..842ac65abc08 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -453,6 +453,8 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count, > * secid in the lsmblob structure. > */ > if (hooks[i].head == &security_hook_heads.audit_rule_match || > + hooks[i].head == > + &security_hook_heads.dentry_init_security || > hooks[i].head == &security_hook_heads.kernel_act_as || > hooks[i].head == > &security_hook_heads.socket_getpeersec_dgram || > @@ -1040,11 +1042,21 @@ void security_inode_free(struct inode *inode) > } > > int security_dentry_init_security(struct dentry *dentry, int mode, > - const struct qstr *name, void **ctx, > - u32 *ctxlen) > + const struct qstr *name, > + struct lsmcontext *cp) > { > - return call_int_hook(dentry_init_security, -EOPNOTSUPP, dentry, mode, > - name, ctx, ctxlen); > + int *display = current->security; > + struct security_hook_list *hp; > + > + hlist_for_each_entry(hp, &security_hook_heads.dentry_init_security, > + list) > + if (*display == 0 || *display == hp->slot) { Is this supposed to be == -1 not 0? Isn't 0 an assigned slot? Otherwise: Reviewed-by: Kees Cook -Kees > + cp->slot = hp->slot; > + return hp->hook.dentry_init_security(dentry, mode, > + name, (void **)&cp->context, &cp->len); > + } > + > + return -EOPNOTSUPP; > } > EXPORT_SYMBOL(security_dentry_init_security); > > -- > 2.20.1 > -- Kees Cook