From: Stephen Smalley <sds@epoch.ncsc.mil>
This patch adds new permission checks to the SELinux mmap and mprotect hooks
to enable control over the ability to make executable a mapping that can
contain data not covered by the existing file-based permission checks.
The task->self execmem permission controls the ability to create an executable
anonymous mapping or a writable executable private file mapping. The
task->file execmod permission controls the ability to make executable a
previously written private file mapping, e.g. for text relocations. Thanks
to Roland McGrath for input and feedback on earlier versions of this patch.
Signed-off-by: Stephen Smalley <sds@epoch.ncsc.mil>
Signed-off-by: James Morris <jmorris@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/security/selinux/hooks.c | 23 +++++++++++++++++++
25-akpm/security/selinux/include/av_perm_to_string.h | 2 +
25-akpm/security/selinux/include/av_permissions.h | 2 +
3 files changed, 27 insertions(+)
diff -puN security/selinux/hooks.c~selinux-enhance-selinux-control-of-executable-mappings security/selinux/hooks.c
--- 25/security/selinux/hooks.c~selinux-enhance-selinux-control-of-executable-mappings Thu Dec 2 12:56:50 2004
+++ 25-akpm/security/selinux/hooks.c Thu Dec 2 12:56:50 2004
@@ -2443,6 +2443,17 @@ static int selinux_file_ioctl(struct fil
static int file_map_prot_check(struct file *file, unsigned long prot, int shared)
{
+ if ((prot & PROT_EXEC) && (!file || (!shared && (prot & PROT_WRITE)))) {
+ /*
+ * We are making executable an anonymous mapping or a
+ * private file mapping that will also be writable.
+ * This has an additional check.
+ */
+ int rc = task_has_perm(current, current, PROCESS__EXECMEM);
+ if (rc)
+ return rc;
+ }
+
if (file) {
/* read access is always possible with a mapping */
u32 av = FILE__READ;
@@ -2480,6 +2491,18 @@ static int selinux_file_mprotect(struct
if (rc)
return rc;
+ if (vma->vm_file != NULL && vma->anon_vma != NULL && (prot & PROT_EXEC)) {
+ /*
+ * We are making executable a file mapping that has
+ * had some COW done. Since pages might have been written,
+ * check ability to execute the possibly modified content.
+ * This typically should only occur for text relocations.
+ */
+ int rc = file_has_perm(current, vma->vm_file, FILE__EXECMOD);
+ if (rc)
+ return rc;
+ }
+
return file_map_prot_check(vma->vm_file, prot, vma->vm_flags&VM_SHARED);
}
diff -puN security/selinux/include/av_permissions.h~selinux-enhance-selinux-control-of-executable-mappings security/selinux/include/av_permissions.h
--- 25/security/selinux/include/av_permissions.h~selinux-enhance-selinux-control-of-executable-mappings Thu Dec 2 12:56:50 2004
+++ 25-akpm/security/selinux/include/av_permissions.h Thu Dec 2 12:56:50 2004
@@ -105,6 +105,7 @@
#define FILE__EXECUTE_NO_TRANS 0x00020000UL
#define FILE__ENTRYPOINT 0x00040000UL
+#define FILE__EXECMOD 0x00080000UL
#define LNK_FILE__IOCTL 0x00000001UL
#define LNK_FILE__READ 0x00000002UL
@@ -458,6 +459,7 @@
#define PROCESS__RLIMITINH 0x00400000UL
#define PROCESS__DYNTRANSITION 0x00800000UL
#define PROCESS__SETCURRENT 0x01000000UL
+#define PROCESS__EXECMEM 0x02000000UL
#define IPC__CREATE 0x00000001UL
#define IPC__DESTROY 0x00000002UL
diff -puN security/selinux/include/av_perm_to_string.h~selinux-enhance-selinux-control-of-executable-mappings security/selinux/include/av_perm_to_string.h
--- 25/security/selinux/include/av_perm_to_string.h~selinux-enhance-selinux-control-of-executable-mappings Thu Dec 2 12:56:50 2004
+++ 25-akpm/security/selinux/include/av_perm_to_string.h Thu Dec 2 12:56:50 2004
@@ -16,6 +16,7 @@
S_(SECCLASS_DIR, DIR__RMDIR, "rmdir")
S_(SECCLASS_FILE, FILE__EXECUTE_NO_TRANS, "execute_no_trans")
S_(SECCLASS_FILE, FILE__ENTRYPOINT, "entrypoint")
+ S_(SECCLASS_FILE, FILE__EXECMOD, "execmod")
S_(SECCLASS_FD, FD__USE, "use")
S_(SECCLASS_TCP_SOCKET, TCP_SOCKET__CONNECTTO, "connectto")
S_(SECCLASS_TCP_SOCKET, TCP_SOCKET__NEWCONN, "newconn")
@@ -64,6 +65,7 @@
S_(SECCLASS_PROCESS, PROCESS__RLIMITINH, "rlimitinh")
S_(SECCLASS_PROCESS, PROCESS__DYNTRANSITION, "dyntransition")
S_(SECCLASS_PROCESS, PROCESS__SETCURRENT, "setcurrent")
+ S_(SECCLASS_PROCESS, PROCESS__EXECMEM, "execmem")
S_(SECCLASS_MSGQ, MSGQ__ENQUEUE, "enqueue")
S_(SECCLASS_MSG, MSG__SEND, "send")
S_(SECCLASS_MSG, MSG__RECEIVE, "receive")
_