diff options
Diffstat (limited to 'mm/shmem.c')
| -rw-r--r-- | mm/shmem.c | 369 |
1 files changed, 349 insertions, 20 deletions
@@ -66,6 +66,9 @@ static struct vfsmount *shm_mnt; #include <linux/highmem.h> #include <linux/seq_file.h> #include <linux/magic.h> +#include <linux/syscalls.h> +#include <linux/fcntl.h> +#include <uapi/linux/memfd.h> #include <asm/uaccess.h> #include <asm/pgtable.h> @@ -419,7 +422,6 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, pvec.pages, indices); if (!pvec.nr) break; - mem_cgroup_uncharge_start(); for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; @@ -447,7 +449,6 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, } pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); - mem_cgroup_uncharge_end(); cond_resched(); index++; } @@ -495,7 +496,6 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, index = start; continue; } - mem_cgroup_uncharge_start(); for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; @@ -531,7 +531,6 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, } pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); - mem_cgroup_uncharge_end(); index++; } @@ -551,6 +550,7 @@ EXPORT_SYMBOL_GPL(shmem_truncate_range); 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); @@ -561,6 +561,11 @@ static int shmem_setattr(struct dentry *dentry, struct iattr *attr) 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) { error = shmem_reacct_size(SHMEM_I(inode)->flags, oldsize, newsize); @@ -621,7 +626,7 @@ static int shmem_unuse_inode(struct shmem_inode_info *info, radswap = swp_to_radix_entry(swap); index = radix_tree_locate_item(&mapping->page_tree, radswap); if (index == -1) - return 0; + return -EAGAIN; /* tell shmem_unuse we found nothing */ /* * Move _head_ to start search for next from here. @@ -680,7 +685,6 @@ static int shmem_unuse_inode(struct shmem_inode_info *info, spin_unlock(&info->lock); swap_free(swap); } - error = 1; /* not an error, but entry was found */ } return error; } @@ -692,7 +696,7 @@ int shmem_unuse(swp_entry_t swap, struct page *page) { struct list_head *this, *next; struct shmem_inode_info *info; - int found = 0; + struct mem_cgroup *memcg; int error = 0; /* @@ -707,26 +711,32 @@ int shmem_unuse(swp_entry_t swap, struct page *page) * the shmem_swaplist_mutex which might hold up shmem_writepage(). * Charged back to the user (not to caller) when swap account is used. */ - error = mem_cgroup_charge_file(page, current->mm, GFP_KERNEL); + error = mem_cgroup_try_charge(page, current->mm, GFP_KERNEL, &memcg); if (error) goto out; /* No radix_tree_preload: swap entry keeps a place for page in tree */ + error = -EAGAIN; mutex_lock(&shmem_swaplist_mutex); list_for_each_safe(this, next, &shmem_swaplist) { info = list_entry(this, struct shmem_inode_info, swaplist); if (info->swapped) - found = shmem_unuse_inode(info, swap, &page); + error = shmem_unuse_inode(info, swap, &page); else list_del_init(&info->swaplist); cond_resched(); - if (found) + if (error != -EAGAIN) break; + /* found nothing in this: move on to search the next */ } mutex_unlock(&shmem_swaplist_mutex); - if (found < 0) - error = found; + if (error) { + if (error != -ENOMEM) + error = 0; + mem_cgroup_cancel_charge(page, memcg); + } else + mem_cgroup_commit_charge(page, memcg, true); out: unlock_page(page); page_cache_release(page); @@ -830,7 +840,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) } mutex_unlock(&shmem_swaplist_mutex); - swapcache_free(swap, NULL); + swapcache_free(swap); redirty: set_page_dirty(page); if (wbc->for_reclaim) @@ -1003,7 +1013,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp, */ oldpage = newpage; } else { - mem_cgroup_replace_page_cache(oldpage, newpage); + mem_cgroup_migrate(oldpage, newpage, false); lru_cache_add_anon(newpage); *pagep = newpage; } @@ -1030,6 +1040,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, struct address_space *mapping = inode->i_mapping; struct shmem_inode_info *info; struct shmem_sb_info *sbinfo; + struct mem_cgroup *memcg; struct page *page; swp_entry_t swap; int error; @@ -1108,8 +1119,7 @@ repeat: goto failed; } - error = mem_cgroup_charge_file(page, current->mm, - gfp & GFP_RECLAIM_MASK); + error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg); if (!error) { error = shmem_add_to_page_cache(page, mapping, index, swp_to_radix_entry(swap)); @@ -1125,12 +1135,16 @@ repeat: * Reset swap.val? No, leave it so "failed" goes back to * "repeat": reading a hole and writing should succeed. */ - if (error) + if (error) { + mem_cgroup_cancel_charge(page, memcg); delete_from_swap_cache(page); + } } if (error) goto failed; + mem_cgroup_commit_charge(page, memcg, true); + spin_lock(&info->lock); info->swapped--; shmem_recalc_inode(inode); @@ -1168,8 +1182,7 @@ repeat: if (sgp == SGP_WRITE) __SetPageReferenced(page); - error = mem_cgroup_charge_file(page, current->mm, - gfp & GFP_RECLAIM_MASK); + error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg); if (error) goto decused; error = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK); @@ -1179,9 +1192,10 @@ repeat: radix_tree_preload_end(); } if (error) { - mem_cgroup_uncharge_cache_page(page); + mem_cgroup_cancel_charge(page, memcg); goto decused; } + mem_cgroup_commit_charge(page, memcg, false); lru_cache_add_anon(page); spin_lock(&info->lock); @@ -1407,6 +1421,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode 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); simple_xattrs_init(&info->xattrs); @@ -1465,7 +1480,17 @@ shmem_write_begin(struct file *file, struct address_space *mapping, 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); } @@ -1803,11 +1828,233 @@ static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence) return offset; } +/* + * We need a tag: a new tag would expand every radix_tree_node by 8 bytes, + * so reuse a tag which we firmly believe is never set or cleared on shmem. + */ +#define SHMEM_TAG_PINNED PAGECACHE_TAG_TOWRITE +#define LAST_SCAN 4 /* about 150ms max */ + +static void shmem_tag_pins(struct address_space *mapping) +{ + struct radix_tree_iter iter; + void **slot; + pgoff_t start; + struct page *page; + + lru_add_drain(); + start = 0; + rcu_read_lock(); + +restart: + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { + page = radix_tree_deref_slot(slot); + if (!page || radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) + goto restart; + } else if (page_count(page) - page_mapcount(page) > 1) { + spin_lock_irq(&mapping->tree_lock); + radix_tree_tag_set(&mapping->page_tree, iter.index, + SHMEM_TAG_PINNED); + spin_unlock_irq(&mapping->tree_lock); + } + + if (need_resched()) { + cond_resched_rcu(); + start = iter.index + 1; + goto restart; + } + } + rcu_read_unlock(); +} + +/* + * Setting SEAL_WRITE requires us to verify there's no pending writer. However, + * via get_user_pages(), drivers might have some pending I/O without any active + * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages + * and see whether it has an elevated ref-count. If so, we tag them and wait for + * them to be dropped. + * The caller must guarantee that no new user will acquire writable references + * to those pages to avoid races. + */ +static int shmem_wait_for_pins(struct address_space *mapping) +{ + struct radix_tree_iter iter; + void **slot; + pgoff_t start; + struct page *page; + int error, scan; + + shmem_tag_pins(mapping); + + error = 0; + for (scan = 0; scan <= LAST_SCAN; scan++) { + if (!radix_tree_tagged(&mapping->page_tree, SHMEM_TAG_PINNED)) + break; + + if (!scan) + lru_add_drain_all(); + else if (schedule_timeout_killable((HZ << scan) / 200)) + scan = LAST_SCAN; + + start = 0; + rcu_read_lock(); +restart: + radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, + start, SHMEM_TAG_PINNED) { + + page = radix_tree_deref_slot(slot); + if (radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) + goto restart; + + page = NULL; + } + + if (page && + page_count(page) - page_mapcount(page) != 1) { + if (scan < LAST_SCAN) + goto continue_resched; + + /* + * On the last scan, we clean up all those tags + * we inserted; but make a note that we still + * found pages pinned. + */ + error = -EBUSY; + } + + spin_lock_irq(&mapping->tree_lock); + radix_tree_tag_clear(&mapping->page_tree, + iter.index, SHMEM_TAG_PINNED); + spin_unlock_irq(&mapping->tree_lock); +continue_resched: + if (need_resched()) { + cond_resched_rcu(); + start = iter.index + 1; + goto restart; + } + } + rcu_read_unlock(); + } + + return error; +} + +#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 long shmem_fallocate(struct file *file, int mode, loff_t offset, loff_t len) { struct inode *inode = file_inode(file); struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); + struct shmem_inode_info *info = SHMEM_I(inode); struct shmem_falloc shmem_falloc; pgoff_t start, index, end; int error; @@ -1823,6 +2070,12 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1; DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq); + /* protected by i_mutex */ + if (info->seals & F_SEAL_WRITE) { + error = -EPERM; + goto out; + } + shmem_falloc.waitq = &shmem_falloc_waitq; shmem_falloc.start = unmap_start >> PAGE_SHIFT; shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT; @@ -1849,6 +2102,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, if (error) goto out; + if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) { + error = -EPERM; + goto out; + } + start = offset >> PAGE_CACHE_SHIFT; end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; /* Try to avoid a swapstorm if len is impossible to satisfy */ @@ -2584,6 +2842,77 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root) shmem_show_mpol(seq, sbinfo->mpol); return 0; } + +#define MFD_NAME_PREFIX "memfd:" +#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1) +#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN) + +#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING) + +SYSCALL_DEFINE2(memfd_create, + const char __user *, uname, + unsigned int, flags) +{ + struct shmem_inode_info *info; + struct file *file; + int fd, error; + char *name; + long len; + + if (flags & ~(unsigned int)MFD_ALL_FLAGS) + return -EINVAL; + + /* length includes terminating zero */ + len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1); + if (len <= 0) + return -EFAULT; + if (len > MFD_NAME_MAX_LEN + 1) + return -EINVAL; + + name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_TEMPORARY); + if (!name) + return -ENOMEM; + + strcpy(name, MFD_NAME_PREFIX); + if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) { + error = -EFAULT; + goto err_name; + } + + /* terminating-zero may have changed after strnlen_user() returned */ + if (name[len + MFD_NAME_PREFIX_LEN - 1]) { + error = -EFAULT; + goto err_name; + } + + fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0); + if (fd < 0) { + error = fd; + goto err_name; + } + + file = shmem_file_setup(name, 0, VM_NORESERVE); + if (IS_ERR(file)) { + error = PTR_ERR(file); + goto err_fd; + } + info = SHMEM_I(file_inode(file)); + file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE; + file->f_flags |= O_RDWR | O_LARGEFILE; + if (flags & MFD_ALLOW_SEALING) + info->seals &= ~F_SEAL_SEAL; + + fd_install(fd, file); + kfree(name); + return fd; + +err_fd: + put_unused_fd(fd); +err_name: + kfree(name); + return error; +} + #endif /* CONFIG_TMPFS */ static void shmem_put_super(struct super_block *sb) |
