From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH 07/32] selinux: Implement the new mount API LSM hooks [ver #9] To: David Howells , viro@zeniv.linux.org.uk Cc: Paul Moore , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org, torvalds@linux-foundation.org References: <153126248868.14533.9751473662727327569.stgit@warthog.procyon.org.uk> <153126253554.14533.643647579195359736.stgit@warthog.procyon.org.uk> From: Stephen Smalley Message-ID: <078bdc66-3726-72ae-cc1e-85290bb7a16a@tycho.nsa.gov> Date: Wed, 11 Jul 2018 10:08:17 -0400 MIME-Version: 1.0 In-Reply-To: <153126253554.14533.643647579195359736.stgit@warthog.procyon.org.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: On 07/10/2018 06:42 PM, David Howells wrote: > Implement the new mount API LSM hooks for SELinux. At some point the old > hooks will need to be removed. > > Question: Should the ->fs_context_parse_source() hook be implemented to > check the labels on any source devices specified? The hook interface doesn't appear to lend itself to such validation, since you are just passing a string, not an inode. Looking up the inode within the security module could easily yield a different object than what is ultimately used for the actual mount. > > Signed-off-by: David Howells > cc: Paul Moore > cc: Stephen Smalley > cc: selinux@tycho.nsa.gov > cc: linux-security-module@vger.kernel.org > --- > > security/selinux/hooks.c | 264 ++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 264 insertions(+) > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 5bb53edd74cc..bdecae4b7306 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -48,6 +48,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -2973,6 +2974,261 @@ static int selinux_umount(struct vfsmount *mnt, int flags) > FILESYSTEM__UNMOUNT, NULL); > } > > +/* fsopen mount context operations */ > + > +static int selinux_fs_context_alloc(struct fs_context *fc, > + struct dentry *reference) > +{ > + struct security_mnt_opts *opts; > + > + opts = kzalloc(sizeof(*opts), GFP_KERNEL); > + if (!opts) > + return -ENOMEM; > + > + fc->security = opts; > + return 0; > +} > + > +static int selinux_fs_context_dup(struct fs_context *fc, > + struct fs_context *src_fc) > +{ > + const struct security_mnt_opts *src = src_fc->security; > + struct security_mnt_opts *opts; > + int i, n; > + > + opts = kzalloc(sizeof(*opts), GFP_KERNEL); > + if (!opts) > + return -ENOMEM; > + fc->security = opts; > + > + if (!src || !src->num_mnt_opts) > + return 0; > + n = opts->num_mnt_opts = src->num_mnt_opts; > + > + if (src->mnt_opts) { > + opts->mnt_opts = kcalloc(n, sizeof(char *), GFP_KERNEL); > + if (!opts->mnt_opts) > + return -ENOMEM; > + > + for (i = 0; i < n; i++) { > + if (src->mnt_opts[i]) { > + opts->mnt_opts[i] = kstrdup(src->mnt_opts[i], > + GFP_KERNEL); > + if (!opts->mnt_opts[i]) > + return -ENOMEM; > + } > + } > + } > + > + if (src->mnt_opts_flags) { > + opts->mnt_opts_flags = kmemdup(src->mnt_opts_flags, > + n * sizeof(int), GFP_KERNEL); > + if (!opts->mnt_opts_flags) > + return -ENOMEM; > + } > + > + return 0; > +} > + > +static void selinux_fs_context_free(struct fs_context *fc) > +{ > + struct security_mnt_opts *opts = fc->security; > + > + if (opts) { > + security_free_mnt_opts(opts); > + fc->security = NULL; > + } > +} > + > +static int selinux_fs_context_parse_option(struct fs_context *fc, char *opt, size_t len) > +{ > + struct security_mnt_opts *opts = fc->security; > + substring_t args[MAX_OPT_ARGS]; > + unsigned int have; > + char *c, **oo; > + int token, ctx, i, *of; > + > + token = match_token(opt, tokens, args); > + if (token == Opt_error) > + return 0; /* Doesn't belong to us. */ > + > + have = 0; > + for (i = 0; i < opts->num_mnt_opts; i++) > + have |= 1 << opts->mnt_opts_flags[i]; > + if (have & (1 << token)) > + return -EINVAL; > + > + switch (token) { > + case Opt_context: > + if (have & (1 << Opt_defcontext)) > + goto incompatible; > + ctx = CONTEXT_MNT; > + goto copy_context_string; > + > + case Opt_fscontext: > + ctx = FSCONTEXT_MNT; > + goto copy_context_string; > + > + case Opt_rootcontext: > + ctx = ROOTCONTEXT_MNT; > + goto copy_context_string; > + > + case Opt_defcontext: > + if (have & (1 << Opt_context)) > + goto incompatible; > + ctx = DEFCONTEXT_MNT; > + goto copy_context_string; > + > + case Opt_labelsupport: > + return 1; > + > + default: > + return -EINVAL; > + } > + > +copy_context_string: > + if (opts->num_mnt_opts > 3) > + return -EINVAL; > + > + of = krealloc(opts->mnt_opts_flags, > + (opts->num_mnt_opts + 1) * sizeof(int), GFP_KERNEL); > + if (!of) > + return -ENOMEM; > + of[opts->num_mnt_opts] = 0; > + opts->mnt_opts_flags = of; > + > + oo = krealloc(opts->mnt_opts, > + (opts->num_mnt_opts + 1) * sizeof(char *), GFP_KERNEL); > + if (!oo) > + return -ENOMEM; > + oo[opts->num_mnt_opts] = NULL; > + opts->mnt_opts = oo; > + > + c = match_strdup(&args[0]); > + if (!c) > + return -ENOMEM; > + opts->mnt_opts[opts->num_mnt_opts] = c; > + opts->mnt_opts_flags[opts->num_mnt_opts] = ctx; > + opts->num_mnt_opts++; > + return 1; > + > +incompatible: > + return -EINVAL; > +} > + > +/* > + * Validate the security parameters supplied for a reconfiguration/remount > + * event. > + */ > +static int selinux_validate_for_sb_reconfigure(struct fs_context *fc) > +{ > + struct super_block *sb = fc->root->d_sb; > + struct superblock_security_struct *sbsec = sb->s_security; > + struct security_mnt_opts *opts = fc->security; > + int rc, i, *flags; > + char **mount_options; > + > + if (!(sbsec->flags & SE_SBINITIALIZED)) > + return 0; > + > + mount_options = opts->mnt_opts; > + flags = opts->mnt_opts_flags; > + > + for (i = 0; i < opts->num_mnt_opts; i++) { > + u32 sid; > + > + if (flags[i] == SBLABEL_MNT) > + continue; > + > + rc = security_context_str_to_sid(&selinux_state, mount_options[i], > + &sid, GFP_KERNEL); > + if (rc) { > + pr_warn("SELinux: security_context_str_to_sid" > + "(%s) failed for (dev %s, type %s) errno=%d\n", > + mount_options[i], sb->s_id, sb->s_type->name, rc); > + goto inval; > + } > + > + switch (flags[i]) { > + case FSCONTEXT_MNT: > + if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid, sid)) > + goto bad_option; > + break; > + case CONTEXT_MNT: > + if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid, sid)) > + goto bad_option; > + break; > + case ROOTCONTEXT_MNT: { > + struct inode_security_struct *root_isec; > + root_isec = backing_inode_security(sb->s_root); > + > + if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid, sid)) > + goto bad_option; > + break; > + } > + case DEFCONTEXT_MNT: > + if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid, sid)) > + goto bad_option; > + break; > + default: > + goto inval; > + } > + } > + > + rc = 0; > +out: > + return rc; > + > +bad_option: > + pr_warn("SELinux: unable to change security options " > + "during remount (dev %s, type=%s)\n", > + sb->s_id, sb->s_type->name); > +inval: > + rc = -EINVAL; > + goto out; > +} > + > +/* > + * Validate the security context assembled from the option data supplied to > + * mount. > + */ > +static int selinux_fs_context_validate(struct fs_context *fc) > +{ > + if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) > + return selinux_validate_for_sb_reconfigure(fc); > + return 0; > +} > + > +/* > + * Set the security context on a superblock. > + */ > +static int selinux_sb_get_tree(struct fs_context *fc) > +{ > + const struct cred *cred = current_cred(); > + struct common_audit_data ad; > + int rc; > + > + rc = selinux_set_mnt_opts(fc->root->d_sb, fc->security, 0, NULL); > + if (rc) > + return rc; > + > + /* Allow all mounts performed by the kernel */ > + if (fc->purpose == FS_CONTEXT_FOR_KERNEL_MOUNT) > + return 0; > + > + ad.type = LSM_AUDIT_DATA_DENTRY; > + ad.u.dentry = fc->root; > + return superblock_has_perm(cred, fc->root->d_sb, FILESYSTEM__MOUNT, &ad); > +} > + > +static int selinux_sb_mountpoint(struct fs_context *fc, struct path *mountpoint, > + unsigned int mnt_flags) > +{ > + const struct cred *cred = current_cred(); > + > + return path_has_perm(cred, mountpoint, FILE__MOUNTON); > +} > + > /* inode security operations */ > > static int selinux_inode_alloc_security(struct inode *inode) > @@ -6905,6 +7161,14 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = { > LSM_HOOK_INIT(bprm_committing_creds, selinux_bprm_committing_creds), > LSM_HOOK_INIT(bprm_committed_creds, selinux_bprm_committed_creds), > > + LSM_HOOK_INIT(fs_context_alloc, selinux_fs_context_alloc), > + LSM_HOOK_INIT(fs_context_dup, selinux_fs_context_dup), > + LSM_HOOK_INIT(fs_context_free, selinux_fs_context_free), > + LSM_HOOK_INIT(fs_context_parse_option, selinux_fs_context_parse_option), > + LSM_HOOK_INIT(fs_context_validate, selinux_fs_context_validate), > + LSM_HOOK_INIT(sb_get_tree, selinux_sb_get_tree), > + LSM_HOOK_INIT(sb_mountpoint, selinux_sb_mountpoint), > + > LSM_HOOK_INIT(sb_alloc_security, selinux_sb_alloc_security), > LSM_HOOK_INIT(sb_free_security, selinux_sb_free_security), > LSM_HOOK_INIT(sb_copy_data, selinux_sb_copy_data), >