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![Elena Reshetova](/assets/img/avatar_default.png)
atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable posix_acl.a_refcount is used as pure reference counter. Convert it to refcount_t and fix up the operations. **Important note for maintainers: Some functions from refcount_t API defined in lib/refcount.c have different memory ordering guarantees than their atomic counterparts. The full comparison can be seen in https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon in state to be merged to the documentation tree. Normally the differences should not matter since refcount_t provides enough guarantees to satisfy the refcounting use cases, but in some rare cases it might matter. Please double check that you don't have some undocumented memory guarantees for this variable usage. For the posix_acl.a_refcount it might make a difference in following places: - get_cached_acl(): increment in refcount_inc_not_zero() only guarantees control dependency on success vs. fully ordered atomic counterpart. However this operation is performed under rcu_read_lock(), so this should be fine. - posix_acl_release(): decrement in refcount_dec_and_test() only provides RELEASE ordering and control dependency on success vs. fully ordered atomic counterpart Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: David Windsor <dwindsor@gmail.com> Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
406 lines
8.9 KiB
C
406 lines
8.9 KiB
C
/*
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* fs/f2fs/acl.c
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*
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* Copyright (c) 2012 Samsung Electronics Co., Ltd.
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* http://www.samsung.com/
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*
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* Portions of this code from linux/fs/ext2/acl.c
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*
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* Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/f2fs_fs.h>
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#include "f2fs.h"
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#include "xattr.h"
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#include "acl.h"
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static inline size_t f2fs_acl_size(int count)
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{
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if (count <= 4) {
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return sizeof(struct f2fs_acl_header) +
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count * sizeof(struct f2fs_acl_entry_short);
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} else {
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return sizeof(struct f2fs_acl_header) +
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4 * sizeof(struct f2fs_acl_entry_short) +
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(count - 4) * sizeof(struct f2fs_acl_entry);
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}
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}
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static inline int f2fs_acl_count(size_t size)
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{
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ssize_t s;
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size -= sizeof(struct f2fs_acl_header);
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s = size - 4 * sizeof(struct f2fs_acl_entry_short);
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if (s < 0) {
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if (size % sizeof(struct f2fs_acl_entry_short))
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return -1;
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return size / sizeof(struct f2fs_acl_entry_short);
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} else {
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if (s % sizeof(struct f2fs_acl_entry))
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return -1;
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return s / sizeof(struct f2fs_acl_entry) + 4;
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}
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}
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static struct posix_acl *f2fs_acl_from_disk(const char *value, size_t size)
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{
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int i, count;
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struct posix_acl *acl;
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struct f2fs_acl_header *hdr = (struct f2fs_acl_header *)value;
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struct f2fs_acl_entry *entry = (struct f2fs_acl_entry *)(hdr + 1);
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const char *end = value + size;
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if (hdr->a_version != cpu_to_le32(F2FS_ACL_VERSION))
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return ERR_PTR(-EINVAL);
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count = f2fs_acl_count(size);
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if (count < 0)
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return ERR_PTR(-EINVAL);
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if (count == 0)
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return NULL;
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acl = posix_acl_alloc(count, GFP_NOFS);
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if (!acl)
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return ERR_PTR(-ENOMEM);
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for (i = 0; i < count; i++) {
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if ((char *)entry > end)
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goto fail;
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acl->a_entries[i].e_tag = le16_to_cpu(entry->e_tag);
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acl->a_entries[i].e_perm = le16_to_cpu(entry->e_perm);
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switch (acl->a_entries[i].e_tag) {
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case ACL_USER_OBJ:
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case ACL_GROUP_OBJ:
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case ACL_MASK:
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case ACL_OTHER:
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entry = (struct f2fs_acl_entry *)((char *)entry +
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sizeof(struct f2fs_acl_entry_short));
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break;
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case ACL_USER:
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acl->a_entries[i].e_uid =
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make_kuid(&init_user_ns,
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le32_to_cpu(entry->e_id));
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entry = (struct f2fs_acl_entry *)((char *)entry +
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sizeof(struct f2fs_acl_entry));
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break;
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case ACL_GROUP:
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acl->a_entries[i].e_gid =
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make_kgid(&init_user_ns,
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le32_to_cpu(entry->e_id));
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entry = (struct f2fs_acl_entry *)((char *)entry +
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sizeof(struct f2fs_acl_entry));
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break;
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default:
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goto fail;
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}
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}
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if ((char *)entry != end)
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goto fail;
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return acl;
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fail:
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posix_acl_release(acl);
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return ERR_PTR(-EINVAL);
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}
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static void *f2fs_acl_to_disk(struct f2fs_sb_info *sbi,
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const struct posix_acl *acl, size_t *size)
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{
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struct f2fs_acl_header *f2fs_acl;
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struct f2fs_acl_entry *entry;
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int i;
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f2fs_acl = f2fs_kmalloc(sbi, sizeof(struct f2fs_acl_header) +
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acl->a_count * sizeof(struct f2fs_acl_entry),
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GFP_NOFS);
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if (!f2fs_acl)
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return ERR_PTR(-ENOMEM);
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f2fs_acl->a_version = cpu_to_le32(F2FS_ACL_VERSION);
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entry = (struct f2fs_acl_entry *)(f2fs_acl + 1);
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for (i = 0; i < acl->a_count; i++) {
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entry->e_tag = cpu_to_le16(acl->a_entries[i].e_tag);
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entry->e_perm = cpu_to_le16(acl->a_entries[i].e_perm);
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switch (acl->a_entries[i].e_tag) {
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case ACL_USER:
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entry->e_id = cpu_to_le32(
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from_kuid(&init_user_ns,
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acl->a_entries[i].e_uid));
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entry = (struct f2fs_acl_entry *)((char *)entry +
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sizeof(struct f2fs_acl_entry));
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break;
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case ACL_GROUP:
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entry->e_id = cpu_to_le32(
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from_kgid(&init_user_ns,
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acl->a_entries[i].e_gid));
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entry = (struct f2fs_acl_entry *)((char *)entry +
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sizeof(struct f2fs_acl_entry));
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break;
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case ACL_USER_OBJ:
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case ACL_GROUP_OBJ:
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case ACL_MASK:
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case ACL_OTHER:
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entry = (struct f2fs_acl_entry *)((char *)entry +
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sizeof(struct f2fs_acl_entry_short));
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break;
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default:
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goto fail;
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}
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}
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*size = f2fs_acl_size(acl->a_count);
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return (void *)f2fs_acl;
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fail:
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kfree(f2fs_acl);
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return ERR_PTR(-EINVAL);
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}
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static struct posix_acl *__f2fs_get_acl(struct inode *inode, int type,
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struct page *dpage)
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{
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int name_index = F2FS_XATTR_INDEX_POSIX_ACL_DEFAULT;
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void *value = NULL;
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struct posix_acl *acl;
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int retval;
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if (type == ACL_TYPE_ACCESS)
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name_index = F2FS_XATTR_INDEX_POSIX_ACL_ACCESS;
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retval = f2fs_getxattr(inode, name_index, "", NULL, 0, dpage);
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if (retval > 0) {
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value = f2fs_kmalloc(F2FS_I_SB(inode), retval, GFP_F2FS_ZERO);
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if (!value)
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return ERR_PTR(-ENOMEM);
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retval = f2fs_getxattr(inode, name_index, "", value,
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retval, dpage);
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}
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if (retval > 0)
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acl = f2fs_acl_from_disk(value, retval);
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else if (retval == -ENODATA)
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acl = NULL;
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else
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acl = ERR_PTR(retval);
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kfree(value);
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return acl;
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}
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struct posix_acl *f2fs_get_acl(struct inode *inode, int type)
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{
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return __f2fs_get_acl(inode, type, NULL);
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}
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static int __f2fs_set_acl(struct inode *inode, int type,
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struct posix_acl *acl, struct page *ipage)
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{
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int name_index;
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void *value = NULL;
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size_t size = 0;
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int error;
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umode_t mode = inode->i_mode;
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switch (type) {
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case ACL_TYPE_ACCESS:
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name_index = F2FS_XATTR_INDEX_POSIX_ACL_ACCESS;
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if (acl && !ipage) {
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error = posix_acl_update_mode(inode, &mode, &acl);
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if (error)
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return error;
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set_acl_inode(inode, mode);
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}
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break;
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case ACL_TYPE_DEFAULT:
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name_index = F2FS_XATTR_INDEX_POSIX_ACL_DEFAULT;
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if (!S_ISDIR(inode->i_mode))
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return acl ? -EACCES : 0;
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break;
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default:
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return -EINVAL;
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}
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if (acl) {
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value = f2fs_acl_to_disk(F2FS_I_SB(inode), acl, &size);
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if (IS_ERR(value)) {
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clear_inode_flag(inode, FI_ACL_MODE);
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return PTR_ERR(value);
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}
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}
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error = f2fs_setxattr(inode, name_index, "", value, size, ipage, 0);
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kfree(value);
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if (!error)
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set_cached_acl(inode, type, acl);
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clear_inode_flag(inode, FI_ACL_MODE);
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return error;
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}
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int f2fs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
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{
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if (unlikely(f2fs_cp_error(F2FS_I_SB(inode))))
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return -EIO;
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return __f2fs_set_acl(inode, type, acl, NULL);
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}
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/*
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* Most part of f2fs_acl_clone, f2fs_acl_create_masq, f2fs_acl_create
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* are copied from posix_acl.c
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*/
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static struct posix_acl *f2fs_acl_clone(const struct posix_acl *acl,
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gfp_t flags)
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{
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struct posix_acl *clone = NULL;
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if (acl) {
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int size = sizeof(struct posix_acl) + acl->a_count *
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sizeof(struct posix_acl_entry);
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clone = kmemdup(acl, size, flags);
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if (clone)
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refcount_set(&clone->a_refcount, 1);
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}
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return clone;
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}
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static int f2fs_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
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{
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struct posix_acl_entry *pa, *pe;
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struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
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umode_t mode = *mode_p;
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int not_equiv = 0;
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/* assert(atomic_read(acl->a_refcount) == 1); */
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FOREACH_ACL_ENTRY(pa, acl, pe) {
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switch(pa->e_tag) {
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case ACL_USER_OBJ:
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pa->e_perm &= (mode >> 6) | ~S_IRWXO;
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mode &= (pa->e_perm << 6) | ~S_IRWXU;
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break;
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case ACL_USER:
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case ACL_GROUP:
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not_equiv = 1;
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break;
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case ACL_GROUP_OBJ:
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group_obj = pa;
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break;
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case ACL_OTHER:
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pa->e_perm &= mode | ~S_IRWXO;
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mode &= pa->e_perm | ~S_IRWXO;
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break;
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case ACL_MASK:
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mask_obj = pa;
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not_equiv = 1;
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break;
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default:
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return -EIO;
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}
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}
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if (mask_obj) {
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mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
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mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
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} else {
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if (!group_obj)
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return -EIO;
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group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
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mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
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}
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*mode_p = (*mode_p & ~S_IRWXUGO) | mode;
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return not_equiv;
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}
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static int f2fs_acl_create(struct inode *dir, umode_t *mode,
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struct posix_acl **default_acl, struct posix_acl **acl,
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struct page *dpage)
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{
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struct posix_acl *p;
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struct posix_acl *clone;
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int ret;
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*acl = NULL;
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*default_acl = NULL;
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if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
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return 0;
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p = __f2fs_get_acl(dir, ACL_TYPE_DEFAULT, dpage);
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if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
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*mode &= ~current_umask();
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return 0;
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}
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if (IS_ERR(p))
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return PTR_ERR(p);
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clone = f2fs_acl_clone(p, GFP_NOFS);
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if (!clone)
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goto no_mem;
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ret = f2fs_acl_create_masq(clone, mode);
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if (ret < 0)
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goto no_mem_clone;
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if (ret == 0)
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posix_acl_release(clone);
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else
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*acl = clone;
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if (!S_ISDIR(*mode))
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posix_acl_release(p);
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else
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*default_acl = p;
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return 0;
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no_mem_clone:
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posix_acl_release(clone);
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no_mem:
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posix_acl_release(p);
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return -ENOMEM;
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}
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int f2fs_init_acl(struct inode *inode, struct inode *dir, struct page *ipage,
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struct page *dpage)
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{
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struct posix_acl *default_acl = NULL, *acl = NULL;
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int error = 0;
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error = f2fs_acl_create(dir, &inode->i_mode, &default_acl, &acl, dpage);
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if (error)
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return error;
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f2fs_mark_inode_dirty_sync(inode, true);
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if (default_acl) {
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error = __f2fs_set_acl(inode, ACL_TYPE_DEFAULT, default_acl,
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ipage);
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posix_acl_release(default_acl);
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}
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if (acl) {
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if (!error)
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error = __f2fs_set_acl(inode, ACL_TYPE_ACCESS, acl,
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ipage);
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posix_acl_release(acl);
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}
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return error;
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}
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