[PATCH] SELinux: decouple fscontext/context mount options
Remove the conflict between fscontext and context mount options. If
context= is specified without fscontext it will operate just as before, if
both are specified we will use mount point labeling and all inodes will get
the label specified by context=. The superblock will be labeled with the
label of fscontext=, thus affecting operations which check the superblock
security context, such as associate permissions.
Signed-off-by: Eric Paris <eparis@parisplace.org>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 24caaee..7e101db 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -246,6 +246,7 @@
sbsec->sb = sb;
sbsec->sid = SECINITSID_UNLABELED;
sbsec->def_sid = SECINITSID_FILE;
+ sbsec->mntpoint_sid = SECINITSID_UNLABELED;
sb->s_security = sbsec;
return 0;
@@ -329,9 +330,26 @@
#define SEL_MOUNT_FAIL_MSG "SELinux: duplicate or incompatible mount options\n"
+static int may_context_mount_sb_relabel(u32 sid,
+ struct superblock_security_struct *sbsec,
+ struct task_security_struct *tsec)
+{
+ int rc;
+
+ rc = avc_has_perm(tsec->sid, sbsec->sid, SECCLASS_FILESYSTEM,
+ FILESYSTEM__RELABELFROM, NULL);
+ if (rc)
+ return rc;
+
+ rc = avc_has_perm(tsec->sid, sid, SECCLASS_FILESYSTEM,
+ FILESYSTEM__RELABELTO, NULL);
+ return rc;
+}
+
static int try_context_mount(struct super_block *sb, void *data)
{
char *context = NULL, *defcontext = NULL;
+ char *fscontext = NULL;
const char *name;
u32 sid;
int alloc = 0, rc = 0, seen = 0;
@@ -374,7 +392,7 @@
switch (token) {
case Opt_context:
- if (seen) {
+ if (seen & (Opt_context|Opt_defcontext)) {
rc = -EINVAL;
printk(KERN_WARNING SEL_MOUNT_FAIL_MSG);
goto out_free;
@@ -390,13 +408,13 @@
break;
case Opt_fscontext:
- if (seen & (Opt_context|Opt_fscontext)) {
+ if (seen & Opt_fscontext) {
rc = -EINVAL;
printk(KERN_WARNING SEL_MOUNT_FAIL_MSG);
goto out_free;
}
- context = match_strdup(&args[0]);
- if (!context) {
+ fscontext = match_strdup(&args[0]);
+ if (!fscontext) {
rc = -ENOMEM;
goto out_free;
}
@@ -441,6 +459,28 @@
if (!seen)
goto out;
+ /* sets the context of the superblock for the fs being mounted. */
+ if (fscontext) {
+ rc = security_context_to_sid(fscontext, strlen(fscontext), &sid);
+ if (rc) {
+ printk(KERN_WARNING "SELinux: security_context_to_sid"
+ "(%s) failed for (dev %s, type %s) errno=%d\n",
+ fscontext, sb->s_id, name, rc);
+ goto out_free;
+ }
+
+ rc = may_context_mount_sb_relabel(sid, sbsec, tsec);
+ if (rc)
+ goto out_free;
+
+ sbsec->sid = sid;
+ }
+
+ /*
+ * Switch to using mount point labeling behavior.
+ * sets the label used on all file below the mountpoint, and will set
+ * the superblock context if not already set.
+ */
if (context) {
rc = security_context_to_sid(context, strlen(context), &sid);
if (rc) {
@@ -450,20 +490,15 @@
goto out_free;
}
- rc = avc_has_perm(tsec->sid, sbsec->sid, SECCLASS_FILESYSTEM,
- FILESYSTEM__RELABELFROM, NULL);
+ rc = may_context_mount_sb_relabel(sid, sbsec, tsec);
if (rc)
goto out_free;
- rc = avc_has_perm(tsec->sid, sid, SECCLASS_FILESYSTEM,
- FILESYSTEM__RELABELTO, NULL);
- if (rc)
- goto out_free;
+ if (!fscontext)
+ sbsec->sid = sid;
+ sbsec->mntpoint_sid = sid;
- sbsec->sid = sid;
-
- if (seen & Opt_context)
- sbsec->behavior = SECURITY_FS_USE_MNTPOINT;
+ sbsec->behavior = SECURITY_FS_USE_MNTPOINT;
}
if (defcontext) {
@@ -495,6 +530,7 @@
if (alloc) {
kfree(context);
kfree(defcontext);
+ kfree(fscontext);
}
out:
return rc;
@@ -876,8 +912,11 @@
goto out;
isec->sid = sid;
break;
+ case SECURITY_FS_USE_MNTPOINT:
+ isec->sid = sbsec->mntpoint_sid;
+ break;
default:
- /* Default to the fs SID. */
+ /* Default to the fs superblock SID. */
isec->sid = sbsec->sid;
if (sbsec->proc) {