@@ -806,7 +806,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
for (i = 0; i < loc->elf_ex.e_phnum; i++, elf_ppnt++)
switch (elf_ppnt->p_type) {
case PT_GNU_STACK:
- if (elf_ppnt->p_flags & PF_X)
+ if (elf_ppnt->p_flags & PF_X &&
+ !security_check_vmflags(VM_EXEC|VM_READ|VM_WRITE))
executable_stack = EXSTACK_ENABLE_X;
else
executable_stack = EXSTACK_DISABLE_X;
@@ -163,7 +163,8 @@ static int elf_fdpic_fetch_phdrs(struct elf_fdpic_params *params,
if (phdr->p_type != PT_GNU_STACK)
continue;
- if (phdr->p_flags & PF_X)
+ if (phdr->p_flags & PF_X &&
+ !security_check_vmflags(VM_EXEC|VM_READ|VM_WRITE))
params->flags |= ELF_FDPIC_FLAG_EXEC_STACK;
else
params->flags |= ELF_FDPIC_FLAG_NOEXEC_STACK;
@@ -756,6 +756,10 @@ int setup_arg_pages(struct linux_binprm *bprm,
vm_flags |= mm->def_flags;
vm_flags |= VM_STACK_INCOMPLETE_SETUP;
+ ret = security_check_vmflags(vm_flags);
+ if (ret)
+ goto out_unlock;
+
ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
vm_flags);
if (ret)
@@ -513,6 +513,11 @@
* @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 the hook mediates both flock and fcntl style locks.
@@ -1597,6 +1602,7 @@
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);
@@ -1897,6 +1903,7 @@ struct security_hook_heads {
struct hlist_head mmap_addr;
struct hlist_head mmap_file;
struct hlist_head file_mprotect;
+ struct hlist_head check_vmflags;
struct hlist_head file_lock;
struct hlist_head file_fcntl;
struct hlist_head file_set_fowner;
@@ -312,6 +312,7 @@ 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);
@@ -859,6 +860,11 @@ 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;
@@ -1390,6 +1390,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
{
struct mm_struct *mm = current->mm;
int pkey = 0;
+ int error;
*populate = 0;
@@ -1453,6 +1454,10 @@ 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;
@@ -2996,6 +3001,10 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla
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;
@@ -3393,6 +3402,10 @@ 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 = vm_area_alloc(mm);
if (unlikely(vma == NULL))
return ERR_PTR(-ENOMEM);
@@ -1421,6 +1421,11 @@ 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);
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", "__install_special_mapping" and "setup_arg_pages". When loading an ELF, this hook is also used to determine what to do with an RWE PT_GNU_STACK header. This allows LSM to force the loader to silently ignore executable stack markings, which is useful a thing to do when trampoline emulation is available. Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com> --- fs/binfmt_elf.c | 3 ++- fs/binfmt_elf_fdpic.c | 3 ++- fs/exec.c | 4 ++++ include/linux/lsm_hooks.h | 7 +++++++ include/linux/security.h | 6 ++++++ mm/mmap.c | 13 +++++++++++++ security/security.c | 5 +++++ 7 files changed, 39 insertions(+), 2 deletions(-)