linux/fs/erofs/xattr.c
Gao Xiang ce06312918 erofs: initialized fields can only be observed after bit is set
Currently, although set_bit() & test_bit() pairs are used as a fast-
path for initialized configurations. However, these atomic ops are
actually relaxed forms. Instead, load-acquire & store-release form is
needed to make sure uninitialized fields won't be observed in advance
here (yet no such corresponding bitops so use full barriers instead.)

Link: https://lore.kernel.org/r/20210209130618.15838-1-hsiangkao@aol.com
Fixes: 62dc45979f ("staging: erofs: fix race of initializing xattrs of a inode at the same time")
Fixes: 152a333a58 ("staging: erofs: add compacted compression indexes support")
Cc: <stable@vger.kernel.org> # 5.3+
Reported-by: Huang Jianan <huangjianan@oppo.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
2021-02-11 11:55:28 +08:00

713 lines
17 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2017-2018 HUAWEI, Inc.
* https://www.huawei.com/
* Created by Gao Xiang <gaoxiang25@huawei.com>
*/
#include <linux/security.h>
#include "xattr.h"
struct xattr_iter {
struct super_block *sb;
struct page *page;
void *kaddr;
erofs_blk_t blkaddr;
unsigned int ofs;
};
static inline void xattr_iter_end(struct xattr_iter *it, bool atomic)
{
/* the only user of kunmap() is 'init_inode_xattrs' */
if (!atomic)
kunmap(it->page);
else
kunmap_atomic(it->kaddr);
unlock_page(it->page);
put_page(it->page);
}
static inline void xattr_iter_end_final(struct xattr_iter *it)
{
if (!it->page)
return;
xattr_iter_end(it, true);
}
static int init_inode_xattrs(struct inode *inode)
{
struct erofs_inode *const vi = EROFS_I(inode);
struct xattr_iter it;
unsigned int i;
struct erofs_xattr_ibody_header *ih;
struct super_block *sb;
struct erofs_sb_info *sbi;
bool atomic_map;
int ret = 0;
/* the most case is that xattrs of this inode are initialized. */
if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags)) {
/*
* paired with smp_mb() at the end of the function to ensure
* fields will only be observed after the bit is set.
*/
smp_mb();
return 0;
}
if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_XATTR_BIT, TASK_KILLABLE))
return -ERESTARTSYS;
/* someone has initialized xattrs for us? */
if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags))
goto out_unlock;
/*
* bypass all xattr operations if ->xattr_isize is not greater than
* sizeof(struct erofs_xattr_ibody_header), in detail:
* 1) it is not enough to contain erofs_xattr_ibody_header then
* ->xattr_isize should be 0 (it means no xattr);
* 2) it is just to contain erofs_xattr_ibody_header, which is on-disk
* undefined right now (maybe use later with some new sb feature).
*/
if (vi->xattr_isize == sizeof(struct erofs_xattr_ibody_header)) {
erofs_err(inode->i_sb,
"xattr_isize %d of nid %llu is not supported yet",
vi->xattr_isize, vi->nid);
ret = -EOPNOTSUPP;
goto out_unlock;
} else if (vi->xattr_isize < sizeof(struct erofs_xattr_ibody_header)) {
if (vi->xattr_isize) {
erofs_err(inode->i_sb,
"bogus xattr ibody @ nid %llu", vi->nid);
DBG_BUGON(1);
ret = -EFSCORRUPTED;
goto out_unlock; /* xattr ondisk layout error */
}
ret = -ENOATTR;
goto out_unlock;
}
sb = inode->i_sb;
sbi = EROFS_SB(sb);
it.blkaddr = erofs_blknr(iloc(sbi, vi->nid) + vi->inode_isize);
it.ofs = erofs_blkoff(iloc(sbi, vi->nid) + vi->inode_isize);
it.page = erofs_get_meta_page(sb, it.blkaddr);
if (IS_ERR(it.page)) {
ret = PTR_ERR(it.page);
goto out_unlock;
}
/* read in shared xattr array (non-atomic, see kmalloc below) */
it.kaddr = kmap(it.page);
atomic_map = false;
ih = (struct erofs_xattr_ibody_header *)(it.kaddr + it.ofs);
vi->xattr_shared_count = ih->h_shared_count;
vi->xattr_shared_xattrs = kmalloc_array(vi->xattr_shared_count,
sizeof(uint), GFP_KERNEL);
if (!vi->xattr_shared_xattrs) {
xattr_iter_end(&it, atomic_map);
ret = -ENOMEM;
goto out_unlock;
}
/* let's skip ibody header */
it.ofs += sizeof(struct erofs_xattr_ibody_header);
for (i = 0; i < vi->xattr_shared_count; ++i) {
if (it.ofs >= EROFS_BLKSIZ) {
/* cannot be unaligned */
DBG_BUGON(it.ofs != EROFS_BLKSIZ);
xattr_iter_end(&it, atomic_map);
it.page = erofs_get_meta_page(sb, ++it.blkaddr);
if (IS_ERR(it.page)) {
kfree(vi->xattr_shared_xattrs);
vi->xattr_shared_xattrs = NULL;
ret = PTR_ERR(it.page);
goto out_unlock;
}
it.kaddr = kmap_atomic(it.page);
atomic_map = true;
it.ofs = 0;
}
vi->xattr_shared_xattrs[i] =
le32_to_cpu(*(__le32 *)(it.kaddr + it.ofs));
it.ofs += sizeof(__le32);
}
xattr_iter_end(&it, atomic_map);
/* paired with smp_mb() at the beginning of the function. */
smp_mb();
set_bit(EROFS_I_EA_INITED_BIT, &vi->flags);
out_unlock:
clear_and_wake_up_bit(EROFS_I_BL_XATTR_BIT, &vi->flags);
return ret;
}
/*
* the general idea for these return values is
* if 0 is returned, go on processing the current xattr;
* 1 (> 0) is returned, skip this round to process the next xattr;
* -err (< 0) is returned, an error (maybe ENOXATTR) occurred
* and need to be handled
*/
struct xattr_iter_handlers {
int (*entry)(struct xattr_iter *_it, struct erofs_xattr_entry *entry);
int (*name)(struct xattr_iter *_it, unsigned int processed, char *buf,
unsigned int len);
int (*alloc_buffer)(struct xattr_iter *_it, unsigned int value_sz);
void (*value)(struct xattr_iter *_it, unsigned int processed, char *buf,
unsigned int len);
};
static inline int xattr_iter_fixup(struct xattr_iter *it)
{
if (it->ofs < EROFS_BLKSIZ)
return 0;
xattr_iter_end(it, true);
it->blkaddr += erofs_blknr(it->ofs);
it->page = erofs_get_meta_page(it->sb, it->blkaddr);
if (IS_ERR(it->page)) {
int err = PTR_ERR(it->page);
it->page = NULL;
return err;
}
it->kaddr = kmap_atomic(it->page);
it->ofs = erofs_blkoff(it->ofs);
return 0;
}
static int inline_xattr_iter_begin(struct xattr_iter *it,
struct inode *inode)
{
struct erofs_inode *const vi = EROFS_I(inode);
struct erofs_sb_info *const sbi = EROFS_SB(inode->i_sb);
unsigned int xattr_header_sz, inline_xattr_ofs;
xattr_header_sz = inlinexattr_header_size(inode);
if (xattr_header_sz >= vi->xattr_isize) {
DBG_BUGON(xattr_header_sz > vi->xattr_isize);
return -ENOATTR;
}
inline_xattr_ofs = vi->inode_isize + xattr_header_sz;
it->blkaddr = erofs_blknr(iloc(sbi, vi->nid) + inline_xattr_ofs);
it->ofs = erofs_blkoff(iloc(sbi, vi->nid) + inline_xattr_ofs);
it->page = erofs_get_meta_page(inode->i_sb, it->blkaddr);
if (IS_ERR(it->page))
return PTR_ERR(it->page);
it->kaddr = kmap_atomic(it->page);
return vi->xattr_isize - xattr_header_sz;
}
/*
* Regardless of success or failure, `xattr_foreach' will end up with
* `ofs' pointing to the next xattr item rather than an arbitrary position.
*/
static int xattr_foreach(struct xattr_iter *it,
const struct xattr_iter_handlers *op,
unsigned int *tlimit)
{
struct erofs_xattr_entry entry;
unsigned int value_sz, processed, slice;
int err;
/* 0. fixup blkaddr, ofs, ipage */
err = xattr_iter_fixup(it);
if (err)
return err;
/*
* 1. read xattr entry to the memory,
* since we do EROFS_XATTR_ALIGN
* therefore entry should be in the page
*/
entry = *(struct erofs_xattr_entry *)(it->kaddr + it->ofs);
if (tlimit) {
unsigned int entry_sz = erofs_xattr_entry_size(&entry);
/* xattr on-disk corruption: xattr entry beyond xattr_isize */
if (*tlimit < entry_sz) {
DBG_BUGON(1);
return -EFSCORRUPTED;
}
*tlimit -= entry_sz;
}
it->ofs += sizeof(struct erofs_xattr_entry);
value_sz = le16_to_cpu(entry.e_value_size);
/* handle entry */
err = op->entry(it, &entry);
if (err) {
it->ofs += entry.e_name_len + value_sz;
goto out;
}
/* 2. handle xattr name (ofs will finally be at the end of name) */
processed = 0;
while (processed < entry.e_name_len) {
if (it->ofs >= EROFS_BLKSIZ) {
DBG_BUGON(it->ofs > EROFS_BLKSIZ);
err = xattr_iter_fixup(it);
if (err)
goto out;
it->ofs = 0;
}
slice = min_t(unsigned int, PAGE_SIZE - it->ofs,
entry.e_name_len - processed);
/* handle name */
err = op->name(it, processed, it->kaddr + it->ofs, slice);
if (err) {
it->ofs += entry.e_name_len - processed + value_sz;
goto out;
}
it->ofs += slice;
processed += slice;
}
/* 3. handle xattr value */
processed = 0;
if (op->alloc_buffer) {
err = op->alloc_buffer(it, value_sz);
if (err) {
it->ofs += value_sz;
goto out;
}
}
while (processed < value_sz) {
if (it->ofs >= EROFS_BLKSIZ) {
DBG_BUGON(it->ofs > EROFS_BLKSIZ);
err = xattr_iter_fixup(it);
if (err)
goto out;
it->ofs = 0;
}
slice = min_t(unsigned int, PAGE_SIZE - it->ofs,
value_sz - processed);
op->value(it, processed, it->kaddr + it->ofs, slice);
it->ofs += slice;
processed += slice;
}
out:
/* xattrs should be 4-byte aligned (on-disk constraint) */
it->ofs = EROFS_XATTR_ALIGN(it->ofs);
return err < 0 ? err : 0;
}
struct getxattr_iter {
struct xattr_iter it;
char *buffer;
int buffer_size, index;
struct qstr name;
};
static int xattr_entrymatch(struct xattr_iter *_it,
struct erofs_xattr_entry *entry)
{
struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);
return (it->index != entry->e_name_index ||
it->name.len != entry->e_name_len) ? -ENOATTR : 0;
}
static int xattr_namematch(struct xattr_iter *_it,
unsigned int processed, char *buf, unsigned int len)
{
struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);
return memcmp(buf, it->name.name + processed, len) ? -ENOATTR : 0;
}
static int xattr_checkbuffer(struct xattr_iter *_it,
unsigned int value_sz)
{
struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);
int err = it->buffer_size < value_sz ? -ERANGE : 0;
it->buffer_size = value_sz;
return !it->buffer ? 1 : err;
}
static void xattr_copyvalue(struct xattr_iter *_it,
unsigned int processed,
char *buf, unsigned int len)
{
struct getxattr_iter *it = container_of(_it, struct getxattr_iter, it);
memcpy(it->buffer + processed, buf, len);
}
static const struct xattr_iter_handlers find_xattr_handlers = {
.entry = xattr_entrymatch,
.name = xattr_namematch,
.alloc_buffer = xattr_checkbuffer,
.value = xattr_copyvalue
};
static int inline_getxattr(struct inode *inode, struct getxattr_iter *it)
{
int ret;
unsigned int remaining;
ret = inline_xattr_iter_begin(&it->it, inode);
if (ret < 0)
return ret;
remaining = ret;
while (remaining) {
ret = xattr_foreach(&it->it, &find_xattr_handlers, &remaining);
if (ret != -ENOATTR)
break;
}
xattr_iter_end_final(&it->it);
return ret ? ret : it->buffer_size;
}
static int shared_getxattr(struct inode *inode, struct getxattr_iter *it)
{
struct erofs_inode *const vi = EROFS_I(inode);
struct super_block *const sb = inode->i_sb;
struct erofs_sb_info *const sbi = EROFS_SB(sb);
unsigned int i;
int ret = -ENOATTR;
for (i = 0; i < vi->xattr_shared_count; ++i) {
erofs_blk_t blkaddr =
xattrblock_addr(sbi, vi->xattr_shared_xattrs[i]);
it->it.ofs = xattrblock_offset(sbi, vi->xattr_shared_xattrs[i]);
if (!i || blkaddr != it->it.blkaddr) {
if (i)
xattr_iter_end(&it->it, true);
it->it.page = erofs_get_meta_page(sb, blkaddr);
if (IS_ERR(it->it.page))
return PTR_ERR(it->it.page);
it->it.kaddr = kmap_atomic(it->it.page);
it->it.blkaddr = blkaddr;
}
ret = xattr_foreach(&it->it, &find_xattr_handlers, NULL);
if (ret != -ENOATTR)
break;
}
if (vi->xattr_shared_count)
xattr_iter_end_final(&it->it);
return ret ? ret : it->buffer_size;
}
static bool erofs_xattr_user_list(struct dentry *dentry)
{
return test_opt(&EROFS_SB(dentry->d_sb)->ctx, XATTR_USER);
}
static bool erofs_xattr_trusted_list(struct dentry *dentry)
{
return capable(CAP_SYS_ADMIN);
}
int erofs_getxattr(struct inode *inode, int index,
const char *name,
void *buffer, size_t buffer_size)
{
int ret;
struct getxattr_iter it;
if (!name)
return -EINVAL;
ret = init_inode_xattrs(inode);
if (ret)
return ret;
it.index = index;
it.name.len = strlen(name);
if (it.name.len > EROFS_NAME_LEN)
return -ERANGE;
it.name.name = name;
it.buffer = buffer;
it.buffer_size = buffer_size;
it.it.sb = inode->i_sb;
ret = inline_getxattr(inode, &it);
if (ret == -ENOATTR)
ret = shared_getxattr(inode, &it);
return ret;
}
static int erofs_xattr_generic_get(const struct xattr_handler *handler,
struct dentry *unused, struct inode *inode,
const char *name, void *buffer, size_t size)
{
struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
switch (handler->flags) {
case EROFS_XATTR_INDEX_USER:
if (!test_opt(&sbi->ctx, XATTR_USER))
return -EOPNOTSUPP;
break;
case EROFS_XATTR_INDEX_TRUSTED:
break;
case EROFS_XATTR_INDEX_SECURITY:
break;
default:
return -EINVAL;
}
return erofs_getxattr(inode, handler->flags, name, buffer, size);
}
const struct xattr_handler erofs_xattr_user_handler = {
.prefix = XATTR_USER_PREFIX,
.flags = EROFS_XATTR_INDEX_USER,
.list = erofs_xattr_user_list,
.get = erofs_xattr_generic_get,
};
const struct xattr_handler erofs_xattr_trusted_handler = {
.prefix = XATTR_TRUSTED_PREFIX,
.flags = EROFS_XATTR_INDEX_TRUSTED,
.list = erofs_xattr_trusted_list,
.get = erofs_xattr_generic_get,
};
#ifdef CONFIG_EROFS_FS_SECURITY
const struct xattr_handler __maybe_unused erofs_xattr_security_handler = {
.prefix = XATTR_SECURITY_PREFIX,
.flags = EROFS_XATTR_INDEX_SECURITY,
.get = erofs_xattr_generic_get,
};
#endif
const struct xattr_handler *erofs_xattr_handlers[] = {
&erofs_xattr_user_handler,
#ifdef CONFIG_EROFS_FS_POSIX_ACL
&posix_acl_access_xattr_handler,
&posix_acl_default_xattr_handler,
#endif
&erofs_xattr_trusted_handler,
#ifdef CONFIG_EROFS_FS_SECURITY
&erofs_xattr_security_handler,
#endif
NULL,
};
struct listxattr_iter {
struct xattr_iter it;
struct dentry *dentry;
char *buffer;
int buffer_size, buffer_ofs;
};
static int xattr_entrylist(struct xattr_iter *_it,
struct erofs_xattr_entry *entry)
{
struct listxattr_iter *it =
container_of(_it, struct listxattr_iter, it);
unsigned int prefix_len;
const char *prefix;
const struct xattr_handler *h =
erofs_xattr_handler(entry->e_name_index);
if (!h || (h->list && !h->list(it->dentry)))
return 1;
prefix = xattr_prefix(h);
prefix_len = strlen(prefix);
if (!it->buffer) {
it->buffer_ofs += prefix_len + entry->e_name_len + 1;
return 1;
}
if (it->buffer_ofs + prefix_len
+ entry->e_name_len + 1 > it->buffer_size)
return -ERANGE;
memcpy(it->buffer + it->buffer_ofs, prefix, prefix_len);
it->buffer_ofs += prefix_len;
return 0;
}
static int xattr_namelist(struct xattr_iter *_it,
unsigned int processed, char *buf, unsigned int len)
{
struct listxattr_iter *it =
container_of(_it, struct listxattr_iter, it);
memcpy(it->buffer + it->buffer_ofs, buf, len);
it->buffer_ofs += len;
return 0;
}
static int xattr_skipvalue(struct xattr_iter *_it,
unsigned int value_sz)
{
struct listxattr_iter *it =
container_of(_it, struct listxattr_iter, it);
it->buffer[it->buffer_ofs++] = '\0';
return 1;
}
static const struct xattr_iter_handlers list_xattr_handlers = {
.entry = xattr_entrylist,
.name = xattr_namelist,
.alloc_buffer = xattr_skipvalue,
.value = NULL
};
static int inline_listxattr(struct listxattr_iter *it)
{
int ret;
unsigned int remaining;
ret = inline_xattr_iter_begin(&it->it, d_inode(it->dentry));
if (ret < 0)
return ret;
remaining = ret;
while (remaining) {
ret = xattr_foreach(&it->it, &list_xattr_handlers, &remaining);
if (ret)
break;
}
xattr_iter_end_final(&it->it);
return ret ? ret : it->buffer_ofs;
}
static int shared_listxattr(struct listxattr_iter *it)
{
struct inode *const inode = d_inode(it->dentry);
struct erofs_inode *const vi = EROFS_I(inode);
struct super_block *const sb = inode->i_sb;
struct erofs_sb_info *const sbi = EROFS_SB(sb);
unsigned int i;
int ret = 0;
for (i = 0; i < vi->xattr_shared_count; ++i) {
erofs_blk_t blkaddr =
xattrblock_addr(sbi, vi->xattr_shared_xattrs[i]);
it->it.ofs = xattrblock_offset(sbi, vi->xattr_shared_xattrs[i]);
if (!i || blkaddr != it->it.blkaddr) {
if (i)
xattr_iter_end(&it->it, true);
it->it.page = erofs_get_meta_page(sb, blkaddr);
if (IS_ERR(it->it.page))
return PTR_ERR(it->it.page);
it->it.kaddr = kmap_atomic(it->it.page);
it->it.blkaddr = blkaddr;
}
ret = xattr_foreach(&it->it, &list_xattr_handlers, NULL);
if (ret)
break;
}
if (vi->xattr_shared_count)
xattr_iter_end_final(&it->it);
return ret ? ret : it->buffer_ofs;
}
ssize_t erofs_listxattr(struct dentry *dentry,
char *buffer, size_t buffer_size)
{
int ret;
struct listxattr_iter it;
ret = init_inode_xattrs(d_inode(dentry));
if (ret == -ENOATTR)
return 0;
if (ret)
return ret;
it.dentry = dentry;
it.buffer = buffer;
it.buffer_size = buffer_size;
it.buffer_ofs = 0;
it.it.sb = dentry->d_sb;
ret = inline_listxattr(&it);
if (ret < 0 && ret != -ENOATTR)
return ret;
return shared_listxattr(&it);
}
#ifdef CONFIG_EROFS_FS_POSIX_ACL
struct posix_acl *erofs_get_acl(struct inode *inode, int type)
{
struct posix_acl *acl;
int prefix, rc;
char *value = NULL;
switch (type) {
case ACL_TYPE_ACCESS:
prefix = EROFS_XATTR_INDEX_POSIX_ACL_ACCESS;
break;
case ACL_TYPE_DEFAULT:
prefix = EROFS_XATTR_INDEX_POSIX_ACL_DEFAULT;
break;
default:
return ERR_PTR(-EINVAL);
}
rc = erofs_getxattr(inode, prefix, "", NULL, 0);
if (rc > 0) {
value = kmalloc(rc, GFP_KERNEL);
if (!value)
return ERR_PTR(-ENOMEM);
rc = erofs_getxattr(inode, prefix, "", value, rc);
}
if (rc == -ENOATTR)
acl = NULL;
else if (rc < 0)
acl = ERR_PTR(rc);
else
acl = posix_acl_from_xattr(&init_user_ns, value, rc);
kfree(value);
return acl;
}
#endif