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[172.10.226.31]) by smtp.gmail.com with ESMTPSA id w16sm5445499ilh.35.2021.02.26.19.37.52 (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 26 Feb 2021 19:37:53 -0800 (PST) From: Olga Kornievskaia To: trond.myklebust@hammerspace.com, anna.schumaker@netapp.com Cc: linux-nfs@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org Subject: [PATCH v4 1/3] [security] Add new hook to compare new mount to an existing mount Date: Fri, 26 Feb 2021 22:37:55 -0500 Message-Id: <20210227033755.24460-1-olga.kornievskaia@gmail.com> X-Mailer: git-send-email 2.10.1 (Apple Git-78) In-Reply-To: References: Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: Olga Kornievskaia Add a new hook that takes an existing super block and a new mount with new options and determines if new options confict with an existing mount or not. A filesystem can use this new hook to determine if it can share the an existing superblock with a new superblock for the new mount. Signed-off-by: Olga Kornievskaia Acked-by: Anna Schumaker --- include/linux/lsm_hook_defs.h | 1 + include/linux/lsm_hooks.h | 6 ++++ include/linux/security.h | 8 +++++ security/security.c | 7 +++++ security/selinux/hooks.c | 56 +++++++++++++++++++++++++++++++++++ 5 files changed, 78 insertions(+) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 7aaa753b8608..1b12a5266a51 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -62,6 +62,7 @@ LSM_HOOK(int, 0, sb_alloc_security, struct super_block *sb) LSM_HOOK(void, LSM_RET_VOID, sb_free_security, struct super_block *sb) LSM_HOOK(void, LSM_RET_VOID, sb_free_mnt_opts, void *mnt_opts) LSM_HOOK(int, 0, sb_eat_lsm_opts, char *orig, void **mnt_opts) +LSM_HOOK(int, 0, sb_mnt_opts_compat, struct super_block *sb, void *mnt_opts) LSM_HOOK(int, 0, sb_remount, struct super_block *sb, void *mnt_opts) LSM_HOOK(int, 0, sb_kern_mount, struct super_block *sb) LSM_HOOK(int, 0, sb_show_options, struct seq_file *m, struct super_block *sb) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index a19adef1f088..0de8eb2ea547 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -142,6 +142,12 @@ * @orig the original mount data copied from userspace. * @copy copied data which will be passed to the security module. * Returns 0 if the copy was successful. + * @sb_mnt_opts_compat: + * Determine if the new mount options in @mnt_opts are allowed given + * the existing mounted filesystem at @sb. + * @sb superblock being compared + * @mnt_opts new mount options + * Return 0 if options are compatible. * @sb_remount: * Extracts security system specific mount options and verifies no changes * are being made to those options. diff --git a/include/linux/security.h b/include/linux/security.h index c35ea0ffccd9..50db3d5d1608 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -291,6 +291,7 @@ int security_sb_alloc(struct super_block *sb); void security_sb_free(struct super_block *sb); void security_free_mnt_opts(void **mnt_opts); int security_sb_eat_lsm_opts(char *options, void **mnt_opts); +int security_sb_mnt_opts_compat(struct super_block *sb, void *mnt_opts); int security_sb_remount(struct super_block *sb, void *mnt_opts); int security_sb_kern_mount(struct super_block *sb); int security_sb_show_options(struct seq_file *m, struct super_block *sb); @@ -635,6 +636,13 @@ static inline int security_sb_remount(struct super_block *sb, return 0; } +static inline int security_sb_mnt_opts_compat(struct super_block *sb, + void *mnt_opts) +{ + return 0; +} + + static inline int security_sb_kern_mount(struct super_block *sb) { return 0; diff --git a/security/security.c b/security/security.c index 7b09cfbae94f..56cf5563efde 100644 --- a/security/security.c +++ b/security/security.c @@ -890,6 +890,13 @@ int security_sb_eat_lsm_opts(char *options, void **mnt_opts) } EXPORT_SYMBOL(security_sb_eat_lsm_opts); +int security_sb_mnt_opts_compat(struct super_block *sb, + void *mnt_opts) +{ + return call_int_hook(sb_mnt_opts_compat, 0, sb, mnt_opts); +} +EXPORT_SYMBOL(security_sb_mnt_opts_compat); + int security_sb_remount(struct super_block *sb, void *mnt_opts) { diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 644b17ec9e63..afee3a222a0e 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2656,6 +2656,61 @@ static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts) return rc; } +static int selinux_sb_mnt_opts_compat(struct super_block *sb, void *mnt_opts) +{ + struct selinux_mnt_opts *opts = mnt_opts; + struct superblock_security_struct *sbsec = sb->s_security; + u32 sid; + int rc; + + /* + * Superblock not initialized (i.e. no options) - reject if any + * options specified, otherwise accept. + */ + if (!(sbsec->flags & SE_SBINITIALIZED)) + return opts ? 1 : 0; + + /* + * Superblock initialized and no options specified - reject if + * superblock has any options set, otherwise accept. + */ + if (!opts) + return (sbsec->flags & SE_MNTMASK) ? 1 : 0; + + if (opts->fscontext) { + rc = parse_sid(sb, opts->fscontext, &sid); + if (rc) + return 1; + if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid, sid)) + return 1; + } + if (opts->context) { + rc = parse_sid(sb, opts->context, &sid); + if (rc) + return 1; + if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid, sid)) + return 1; + } + if (opts->rootcontext) { + struct inode_security_struct *root_isec; + + root_isec = backing_inode_security(sb->s_root); + rc = parse_sid(sb, opts->rootcontext, &sid); + if (rc) + return 1; + if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid, sid)) + return 1; + } + if (opts->defcontext) { + rc = parse_sid(sb, opts->defcontext, &sid); + if (rc) + return 1; + if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid, sid)) + return 1; + } + return 0; +} + static int selinux_sb_remount(struct super_block *sb, void *mnt_opts) { struct selinux_mnt_opts *opts = mnt_opts; @@ -6984,6 +7039,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(sb_free_security, selinux_sb_free_security), LSM_HOOK_INIT(sb_free_mnt_opts, selinux_free_mnt_opts), + LSM_HOOK_INIT(sb_mnt_opts_compat, selinux_sb_mnt_opts_compat), LSM_HOOK_INIT(sb_remount, selinux_sb_remount), LSM_HOOK_INIT(sb_kern_mount, selinux_sb_kern_mount), LSM_HOOK_INIT(sb_show_options, selinux_sb_show_options),