In the SECURITY_FS_USE_MNTPOINT case we never want to allow relabeling
files/directories, so we should never set the SBLABEL_MNT flag in this
case. The 'special handling' in selinux_is_sblabel_mnt() is only
intended for SECURITY_FS_USE_GENFS.
While there, make the logic in selinux_is_sblabel_mnt() more explicit
and add a BUILD_BUG_ON() to make sure that introducing a new
SECURITY_FS_USE_* forces a review of the logic.
Note that checkpatch.pl produces some false positives here, likely
having problems recognizing the monstrous return statement...
Fixes: d5f3a5f6e7e7 ("selinux: add security in-core xattr support for pstore and debugfs")
Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
security/selinux/hooks.c | 41 ++++++++++++++++++++++++++++------------
1 file changed, 29 insertions(+), 12 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 7ce012d9ec51..d6d29ec54eab 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -501,19 +501,36 @@ static int selinux_is_sblabel_mnt(struct super_block *sb)
{
struct superblock_security_struct *sbsec = sb->s_security;
- return sbsec->behavior == SECURITY_FS_USE_XATTR ||
- sbsec->behavior == SECURITY_FS_USE_TRANS ||
- sbsec->behavior == SECURITY_FS_USE_TASK ||
- sbsec->behavior == SECURITY_FS_USE_NATIVE ||
+ /*
+ * IMPORTANT: Double-check logic in this function when adding a new
+ * SECURITY_FS_USE_* definition!
+ */
+ BUILD_BUG_ON(SECURITY_FS_USE_MAX != 7);
+
+ switch (sbsec->behavior) {
+ case SECURITY_FS_USE_XATTR:
+ case SECURITY_FS_USE_TRANS:
+ case SECURITY_FS_USE_TASK:
+ case SECURITY_FS_USE_NATIVE:
+ return 1;
+
+ case SECURITY_FS_USE_GENFS:
/* Special handling. Genfs but also in-core setxattr handler */
- !strcmp(sb->s_type->name, "sysfs") ||
- !strcmp(sb->s_type->name, "pstore") ||
- !strcmp(sb->s_type->name, "debugfs") ||
- !strcmp(sb->s_type->name, "tracefs") ||
- !strcmp(sb->s_type->name, "rootfs") ||
- (selinux_policycap_cgroupseclabel() &&
- (!strcmp(sb->s_type->name, "cgroup") ||
- !strcmp(sb->s_type->name, "cgroup2")));
+ return !strcmp(sb->s_type->name, "sysfs") ||
+ !strcmp(sb->s_type->name, "pstore") ||
+ !strcmp(sb->s_type->name, "debugfs") ||
+ !strcmp(sb->s_type->name, "tracefs") ||
+ !strcmp(sb->s_type->name, "rootfs") ||
+ (selinux_policycap_cgroupseclabel() &&
+ (!strcmp(sb->s_type->name, "cgroup") ||
+ !strcmp(sb->s_type->name, "cgroup2")));
+
+ /* Never allow relabeling on context mounts */
+ case SECURITY_FS_USE_MNTPOINT:
+ case SECURITY_FS_USE_NONE:
+ default:
+ return 0;
+ }
}
static int sb_finish_set_opts(struct super_block *sb)
--
2.19.2
