Creation of a new LSM hook to check if a given configuration of vmflags,
for a new memory allocation request, should be allowed or not.
It's placed in "do_mmap", "do_brk_flags" and "__install_special_mapping".
Signed-off-by: Salvatore Mesoraca <s.mesorac...@gmail.com>
---
include/linux/lsm_hooks.h | 7 +++++++
include/linux/security.h | 6 ++++++
mm/mmap.c | 13 +++++++++++++
security/security.c | 5 +++++
4 files changed, 31 insertions(+)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index c5a0322..2fb5c51f 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -484,6 +484,11 @@
* @reqprot contains the protection requested by the application.
* @prot contains the protection that will be applied by the kernel.
* Return 0 if permission is granted.
+ * @check_vmflags:
+ * Check if the requested @vmflags are allowed.
+ * @vmflags contains the requested vmflags.
+ * Return 0 if the operation is allowed to continue otherwise return
+ * the appropriate error code.
* @file_lock:
* Check permission before performing file locking operations.
* Note: this hook mediates both flock and fcntl style locks.
@@ -1496,6 +1501,7 @@
unsigned long prot, unsigned long flags);
int (*file_mprotect)(struct vm_area_struct *vma, unsigned long reqprot,
unsigned long prot);
+ int (*check_vmflags)(vm_flags_t vmflags);
int (*file_lock)(struct file *file, unsigned int cmd);
int (*file_fcntl)(struct file *file, unsigned int cmd,
unsigned long arg);
@@ -1773,6 +1779,7 @@ struct security_hook_heads {
struct list_head mmap_addr;
struct list_head mmap_file;
struct list_head file_mprotect;
+ struct list_head check_vmflags;
struct list_head file_lock;
struct list_head file_fcntl;
struct list_head file_set_fowner;
diff --git a/include/linux/security.h b/include/linux/security.h
index 974bb9b..59840a5 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -309,6 +309,7 @@ int security_mmap_file(struct file *file, unsigned long
prot,
int security_mmap_addr(unsigned long addr);
int security_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
unsigned long prot);
+int security_check_vmflags(vm_flags_t vmflags);
int security_file_lock(struct file *file, unsigned int cmd);
int security_file_fcntl(struct file *file, unsigned int cmd, unsigned long
arg);
void security_file_set_fowner(struct file *file);
@@ -844,6 +845,11 @@ static inline int security_file_mprotect(struct
vm_area_struct *vma,
return 0;
}
+static inline int security_check_vmflags(vm_flags_t vmflags)
+{
+ return 0;
+}
+
static inline int security_file_lock(struct file *file, unsigned int cmd)
{
return 0;
diff --git a/mm/mmap.c b/mm/mmap.c
index 680506f..44bb1a3 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1326,6 +1326,7 @@ unsigned long do_mmap(struct file *file, unsigned long
addr,
{
struct mm_struct *mm = current->mm;
int pkey = 0;
+ int error;
*populate = 0;
@@ -1378,6 +1379,10 @@ unsigned long do_mmap(struct file *file, unsigned long
addr,
vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
+ error = security_check_vmflags(vm_flags);
+ if (error)
+ return error;
+
if (flags & MAP_LOCKED)
if (!can_do_mlock())
return -EPERM;
@@ -2873,6 +2878,10 @@ static int do_brk_flags(unsigned long addr, unsigned
long request, unsigned long
return -EINVAL;
flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
+ error = security_check_vmflags(flags);
+ if (error)
+ return error;
+
error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
if (offset_in_page(error))
return error;
@@ -3269,6 +3278,10 @@ static struct vm_area_struct *__install_special_mapping(
int ret;
struct vm_area_struct *vma;
+ ret = security_check_vmflags(vm_flags);
+ if (ret)
+ return ERR_PTR(ret);
+
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (unlikely(vma == NULL))
return ERR_PTR(-ENOMEM);
diff --git a/security/security.c b/security/security.c
index d482e3d..484143f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -938,6 +938,11 @@ int security_file_mprotect(struct vm_area_struct *vma,
unsigned long reqprot,
return call_int_hook(file_mprotect, 0, vma, reqprot, prot);
}
+int security_check_vmflags(vm_flags_t vmflags)
+{
+ return call_int_hook(check_vmflags, 0, vmflags);
+}
+
int security_file_lock(struct file *file, unsigned int cmd)
{
return call_int_hook(file_lock, 0, file, cmd);
--
1.9.1
