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authorOlga Kornievskaia <kolga@netapp.com>2021-02-26 22:37:55 -0500
committerPaul Moore <paul@paul-moore.com>2021-03-22 14:53:37 -0400
commit69c4a42d72eb9b41e1c6e4bc9ab7f3650bf35f62 (patch)
tree564b363284f41cce68ff9b55a2d0fa811bd8bfcf
parent431c3be16bd08728325814320e3603ec3284d542 (diff)
lsm,selinux: add new hook to compare new mount to an existing mount
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 <kolga@netapp.com> Acked-by: Anna Schumaker <Anna.Schumaker@Netapp.com> [PM: tweak the subject line, fix tab/space problems] Signed-off-by: Paul Moore <paul@paul-moore.com>
-rw-r--r--include/linux/lsm_hook_defs.h1
-rw-r--r--include/linux/lsm_hooks.h6
-rw-r--r--include/linux/security.h8
-rw-r--r--security/security.c7
-rw-r--r--security/selinux/hooks.c56
5 files changed, 78 insertions, 0 deletions
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 477a597db013..1b61bc5dc215 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 fb7f3193753d..97bb36d7e994 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 8aeebd6646dc..f1e5833bfedc 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -294,6 +294,7 @@ 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);
@@ -646,6 +647,13 @@ 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 5ac96b16f8fa..a4e7d50c3e39 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 eca9fc0ba764..07ca2ebf979e 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2685,6 +2685,61 @@ free_opt:
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;
@@ -7078,6 +7133,7 @@ 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),