#include <linux/highmem.h>
#include <linux/seq_file.h>
#include <linux/magic.h>
+#include <linux/fcntl.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
+ struct shmem_inode_info *info = SHMEM_I(inode);
int error;
- error = inode_change_ok(inode, attr);
+ error = setattr_prepare(dentry, attr);
if (error)
return error;
loff_t oldsize = inode->i_size;
loff_t newsize = attr->ia_size;
+ /* protected by i_mutex */
+ if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
+ (newsize > oldsize && (info->seals & F_SEAL_GROW)))
+ return -EPERM;
+
if (newsize != oldsize) {
i_size_write(inode, newsize);
inode->i_ctime = inode->i_mtime = CURRENT_TIME;
mutex_unlock(&inode->i_mutex);
return 0;
}
+EXPORT_SYMBOL_GPL(vmtruncate_range);
#ifdef CONFIG_NUMA
static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
info = SHMEM_I(inode);
memset(info, 0, (char *)inode - (char *)info);
spin_lock_init(&info->lock);
+ info->seals = F_SEAL_SEAL;
info->flags = flags & VM_NORESERVE;
INIT_LIST_HEAD(&info->swaplist);
INIT_LIST_HEAD(&info->xattr_list);
struct page **pagep, void **fsdata)
{
struct inode *inode = mapping->host;
+ struct shmem_inode_info *info = SHMEM_I(inode);
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
+
+ /* i_mutex is held by caller */
+ if (unlikely(info->seals)) {
+ if (info->seals & F_SEAL_WRITE)
+ return -EPERM;
+ if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
+ return -EPERM;
+ }
+
return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
}
return error;
}
+static int shmem_wait_for_pins(struct address_space *mapping)
+{
+ return 0;
+}
+
+#define F_ALL_SEALS (F_SEAL_SEAL | \
+ F_SEAL_SHRINK | \
+ F_SEAL_GROW | \
+ F_SEAL_WRITE)
+
+int shmem_add_seals(struct file *file, unsigned int seals)
+{
+ struct inode *inode = file_inode(file);
+ struct shmem_inode_info *info = SHMEM_I(inode);
+ int error;
+
+ /*
+ * SEALING
+ * Sealing allows multiple parties to share a shmem-file but restrict
+ * access to a specific subset of file operations. Seals can only be
+ * added, but never removed. This way, mutually untrusted parties can
+ * share common memory regions with a well-defined policy. A malicious
+ * peer can thus never perform unwanted operations on a shared object.
+ *
+ * Seals are only supported on special shmem-files and always affect
+ * the whole underlying inode. Once a seal is set, it may prevent some
+ * kinds of access to the file. Currently, the following seals are
+ * defined:
+ * SEAL_SEAL: Prevent further seals from being set on this file
+ * SEAL_SHRINK: Prevent the file from shrinking
+ * SEAL_GROW: Prevent the file from growing
+ * SEAL_WRITE: Prevent write access to the file
+ *
+ * As we don't require any trust relationship between two parties, we
+ * must prevent seals from being removed. Therefore, sealing a file
+ * only adds a given set of seals to the file, it never touches
+ * existing seals. Furthermore, the "setting seals"-operation can be
+ * sealed itself, which basically prevents any further seal from being
+ * added.
+ *
+ * Semantics of sealing are only defined on volatile files. Only
+ * anonymous shmem files support sealing. More importantly, seals are
+ * never written to disk. Therefore, there's no plan to support it on
+ * other file types.
+ */
+
+ if (file->f_op != &shmem_file_operations)
+ return -EINVAL;
+ if (!(file->f_mode & FMODE_WRITE))
+ return -EPERM;
+ if (seals & ~(unsigned int)F_ALL_SEALS)
+ return -EINVAL;
+
+ mutex_lock(&inode->i_mutex);
+
+ if (info->seals & F_SEAL_SEAL) {
+ error = -EPERM;
+ goto unlock;
+ }
+
+ if ((seals & F_SEAL_WRITE) && !(info->seals & F_SEAL_WRITE)) {
+ error = mapping_deny_writable(file->f_mapping);
+ if (error)
+ goto unlock;
+
+ error = shmem_wait_for_pins(file->f_mapping);
+ if (error) {
+ mapping_allow_writable(file->f_mapping);
+ goto unlock;
+ }
+ }
+
+ info->seals |= seals;
+ error = 0;
+
+unlock:
+ mutex_unlock(&inode->i_mutex);
+ return error;
+}
+EXPORT_SYMBOL_GPL(shmem_add_seals);
+
+int shmem_get_seals(struct file *file)
+{
+ if (file->f_op != &shmem_file_operations)
+ return -EINVAL;
+
+ return SHMEM_I(file_inode(file))->seals;
+}
+EXPORT_SYMBOL_GPL(shmem_get_seals);
+
+long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ long error;
+
+ switch (cmd) {
+ case F_ADD_SEALS:
+ /* disallow upper 32bit */
+ if (arg > UINT_MAX)
+ return -EINVAL;
+
+ error = shmem_add_seals(file, arg);
+ break;
+ case F_GET_SEALS:
+ error = shmem_get_seals(file);
+ break;
+ default:
+ error = -EINVAL;
+ break;
+ }
+
+ return error;
+}
+
static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
if (new_dentry->d_inode) {
(void) shmem_unlink(new_dir, new_dentry);
- if (they_are_dirs)
+ if (they_are_dirs) {
+ drop_nlink(new_dentry->d_inode);
drop_nlink(old_dir);
+ }
} else if (they_are_dirs) {
drop_nlink(old_dir);
inc_nlink(new_dir);
vma->vm_flags |= VM_CAN_NONLINEAR;
return 0;
}
+EXPORT_SYMBOL_GPL(shmem_zero_setup);
/**
* shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
git.openpandora.org / pandora-kernel.git / blobdiff