Files can be mmap'ed read/write and later changed to execute to circumvent
IMA's mmap appraise policy rules. Due to locking issues (mmap semaphore
would be taken prior to i_mutex), files can not be measured or appraised at
this point. Eliminate this integrity gap, by denying the mprotect
PROT_EXECUTE change, if an mmap appraise policy rule exists.
On mprotect change success, return 0. On failure, return -EACESS.
Signed-off-by: Mimi Zohar <zo...@linux.ibm.com>
---
include/linux/ima.h | 7 ++++++
security/integrity/ima/ima_main.c | 50 +++++++++++++++++++++++++++++++++++++++
security/security.c | 7 +++++-
3 files changed, 63 insertions(+), 1 deletion(-)
diff --git a/include/linux/ima.h b/include/linux/ima.h
index aefe758f4466..9164e1534ec9 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -18,6 +18,7 @@ extern int ima_file_check(struct file *file, int mask);
extern void ima_post_create_tmpfile(struct inode *inode);
extern void ima_file_free(struct file *file);
extern int ima_file_mmap(struct file *file, unsigned long prot);
+extern int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot);
extern int ima_load_data(enum kernel_load_data_id id);
extern int ima_read_file(struct file *file, enum kernel_read_file_id id);
extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
@@ -70,6 +71,12 @@ static inline int ima_file_mmap(struct file *file, unsigned
long prot)
return 0;
}
+static inline int ima_file_mprotect(struct vm_area_struct *vma,
+ unsigned long prot)
+{
+ return 0;
+}
+
static inline int ima_load_data(enum kernel_load_data_id id)
{
return 0;
diff --git a/security/integrity/ima/ima_main.c
b/security/integrity/ima/ima_main.c
index f96f151294e6..a8706bf7ca25 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -394,6 +394,56 @@ int ima_file_mmap(struct file *file, unsigned long prot)
}
/**
+ * ima_file_mprotect - based on policy, limit mprotect change
+ * @prot: contains the protection that will be applied by the kernel.
+ *
+ * Files can be mmap'ed read/write and later changed to execute to circumvent
+ * IMA's mmap appraisal policy rules. Due to locking issues (mmap semaphore
+ * would be taken before i_mutex), files can not be measured or appraised at
+ * this point. Eliminate this integrity gap by denying the mprotect
+ * PROT_EXECUTE change, if an mmap appraise policy rule exists.
+ *
+ * On mprotect change success, return 0. On failure, return -EACESS.
+ */
+int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
+{
+ struct ima_template_desc *template;
+ struct inode *inode;
+ int result = 0;
+ int action;
+ u32 secid;
+ int pcr;
+
+ if (vma->vm_file && (prot & PROT_EXEC) && !(vma->vm_flags & VM_EXEC)) {
+ inode = file_inode(vma->vm_file);
+
+ security_task_getsecid(current, &secid);
+ action = ima_get_action(inode, current_cred(), secid, MAY_EXEC,
+ MMAP_CHECK, &pcr, &template, 0);
+
+ if (action & IMA_APPRAISE_SUBMASK)
+ result = -EPERM;
+
+ if ((action & IMA_APPRAISE_SUBMASK) || (action & IMA_MEASURE)) {
+ struct file *file = vma->vm_file;
+ char *pathbuf = NULL;
+ const char *pathname;
+ char filename[NAME_MAX];
+
+ pathname = ima_d_path(&file->f_path, &pathbuf,
+ filename);
+ integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
+ pathname, "collect_data",
+ "failed-mprotect", result, 0);
+
+ if (pathbuf)
+ __putname(pathbuf);
+ }
+ }
+ return result;
+}
+
+/**
* ima_bprm_check - based on policy, collect/store measurement.
* @bprm: contains the linux_binprm structure
*
diff --git a/security/security.c b/security/security.c
index 7fed24b9d57e..dd0917c5bfe9 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1512,7 +1512,12 @@ int security_mmap_addr(unsigned long addr)
int security_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
unsigned long prot)
{
- return call_int_hook(file_mprotect, 0, vma, reqprot, prot);
+ int ret;
+
+ ret = call_int_hook(file_mprotect, 0, vma, reqprot, prot);
+ if (ret)
+ return ret;
+ return ima_file_mprotect(vma, prot);
}
int security_file_lock(struct file *file, unsigned int cmd)
--
2.7.5
