linux-stable/fs/sysv/ialloc.c
Christian Brauner 21cb47be6f
inode: make init and permission helpers idmapped mount aware
The inode_owner_or_capable() helper determines whether the caller is the
owner of the inode or is capable with respect to that inode. Allow it to
handle idmapped mounts. If the inode is accessed through an idmapped
mount it according to the mount's user namespace. Afterwards the checks
are identical to non-idmapped mounts. If the initial user namespace is
passed nothing changes so non-idmapped mounts will see identical
behavior as before.

Similarly, allow the inode_init_owner() helper to handle idmapped
mounts. It initializes a new inode on idmapped mounts by mapping the
fsuid and fsgid of the caller from the mount's user namespace. If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-7-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00

235 lines
5.8 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/sysv/ialloc.c
*
* minix/bitmap.c
* Copyright (C) 1991, 1992 Linus Torvalds
*
* ext/freelists.c
* Copyright (C) 1992 Remy Card (card@masi.ibp.fr)
*
* xenix/alloc.c
* Copyright (C) 1992 Doug Evans
*
* coh/alloc.c
* Copyright (C) 1993 Pascal Haible, Bruno Haible
*
* sysv/ialloc.c
* Copyright (C) 1993 Bruno Haible
*
* This file contains code for allocating/freeing inodes.
*/
#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include "sysv.h"
/* We don't trust the value of
sb->sv_sbd2->s_tinode = *sb->sv_sb_total_free_inodes
but we nevertheless keep it up to date. */
/* An inode on disk is considered free if both i_mode == 0 and i_nlink == 0. */
/* return &sb->sv_sb_fic_inodes[i] = &sbd->s_inode[i]; */
static inline sysv_ino_t *
sv_sb_fic_inode(struct super_block * sb, unsigned int i)
{
struct sysv_sb_info *sbi = SYSV_SB(sb);
if (sbi->s_bh1 == sbi->s_bh2)
return &sbi->s_sb_fic_inodes[i];
else {
/* 512 byte Xenix FS */
unsigned int offset = offsetof(struct xenix_super_block, s_inode[i]);
if (offset < 512)
return (sysv_ino_t*)(sbi->s_sbd1 + offset);
else
return (sysv_ino_t*)(sbi->s_sbd2 + offset);
}
}
struct sysv_inode *
sysv_raw_inode(struct super_block *sb, unsigned ino, struct buffer_head **bh)
{
struct sysv_sb_info *sbi = SYSV_SB(sb);
struct sysv_inode *res;
int block = sbi->s_firstinodezone + sbi->s_block_base;
block += (ino-1) >> sbi->s_inodes_per_block_bits;
*bh = sb_bread(sb, block);
if (!*bh)
return NULL;
res = (struct sysv_inode *)(*bh)->b_data;
return res + ((ino-1) & sbi->s_inodes_per_block_1);
}
static int refill_free_cache(struct super_block *sb)
{
struct sysv_sb_info *sbi = SYSV_SB(sb);
struct buffer_head * bh;
struct sysv_inode * raw_inode;
int i = 0, ino;
ino = SYSV_ROOT_INO+1;
raw_inode = sysv_raw_inode(sb, ino, &bh);
if (!raw_inode)
goto out;
while (ino <= sbi->s_ninodes) {
if (raw_inode->i_mode == 0 && raw_inode->i_nlink == 0) {
*sv_sb_fic_inode(sb,i++) = cpu_to_fs16(SYSV_SB(sb), ino);
if (i == sbi->s_fic_size)
break;
}
if ((ino++ & sbi->s_inodes_per_block_1) == 0) {
brelse(bh);
raw_inode = sysv_raw_inode(sb, ino, &bh);
if (!raw_inode)
goto out;
} else
raw_inode++;
}
brelse(bh);
out:
return i;
}
void sysv_free_inode(struct inode * inode)
{
struct super_block *sb = inode->i_sb;
struct sysv_sb_info *sbi = SYSV_SB(sb);
unsigned int ino;
struct buffer_head * bh;
struct sysv_inode * raw_inode;
unsigned count;
sb = inode->i_sb;
ino = inode->i_ino;
if (ino <= SYSV_ROOT_INO || ino > sbi->s_ninodes) {
printk("sysv_free_inode: inode 0,1,2 or nonexistent inode\n");
return;
}
raw_inode = sysv_raw_inode(sb, ino, &bh);
if (!raw_inode) {
printk("sysv_free_inode: unable to read inode block on device "
"%s\n", inode->i_sb->s_id);
return;
}
mutex_lock(&sbi->s_lock);
count = fs16_to_cpu(sbi, *sbi->s_sb_fic_count);
if (count < sbi->s_fic_size) {
*sv_sb_fic_inode(sb,count++) = cpu_to_fs16(sbi, ino);
*sbi->s_sb_fic_count = cpu_to_fs16(sbi, count);
}
fs16_add(sbi, sbi->s_sb_total_free_inodes, 1);
dirty_sb(sb);
memset(raw_inode, 0, sizeof(struct sysv_inode));
mark_buffer_dirty(bh);
mutex_unlock(&sbi->s_lock);
brelse(bh);
}
struct inode * sysv_new_inode(const struct inode * dir, umode_t mode)
{
struct super_block *sb = dir->i_sb;
struct sysv_sb_info *sbi = SYSV_SB(sb);
struct inode *inode;
sysv_ino_t ino;
unsigned count;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE
};
inode = new_inode(sb);
if (!inode)
return ERR_PTR(-ENOMEM);
mutex_lock(&sbi->s_lock);
count = fs16_to_cpu(sbi, *sbi->s_sb_fic_count);
if (count == 0 || (*sv_sb_fic_inode(sb,count-1) == 0)) {
count = refill_free_cache(sb);
if (count == 0) {
iput(inode);
mutex_unlock(&sbi->s_lock);
return ERR_PTR(-ENOSPC);
}
}
/* Now count > 0. */
ino = *sv_sb_fic_inode(sb,--count);
*sbi->s_sb_fic_count = cpu_to_fs16(sbi, count);
fs16_add(sbi, sbi->s_sb_total_free_inodes, -1);
dirty_sb(sb);
inode_init_owner(&init_user_ns, inode, dir, mode);
inode->i_ino = fs16_to_cpu(sbi, ino);
inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
inode->i_blocks = 0;
memset(SYSV_I(inode)->i_data, 0, sizeof(SYSV_I(inode)->i_data));
SYSV_I(inode)->i_dir_start_lookup = 0;
insert_inode_hash(inode);
mark_inode_dirty(inode);
sysv_write_inode(inode, &wbc); /* ensure inode not allocated again */
mark_inode_dirty(inode); /* cleared by sysv_write_inode() */
/* That's it. */
mutex_unlock(&sbi->s_lock);
return inode;
}
unsigned long sysv_count_free_inodes(struct super_block * sb)
{
struct sysv_sb_info *sbi = SYSV_SB(sb);
struct buffer_head * bh;
struct sysv_inode * raw_inode;
int ino, count, sb_count;
mutex_lock(&sbi->s_lock);
sb_count = fs16_to_cpu(sbi, *sbi->s_sb_total_free_inodes);
if (0)
goto trust_sb;
/* this causes a lot of disk traffic ... */
count = 0;
ino = SYSV_ROOT_INO+1;
raw_inode = sysv_raw_inode(sb, ino, &bh);
if (!raw_inode)
goto Eio;
while (ino <= sbi->s_ninodes) {
if (raw_inode->i_mode == 0 && raw_inode->i_nlink == 0)
count++;
if ((ino++ & sbi->s_inodes_per_block_1) == 0) {
brelse(bh);
raw_inode = sysv_raw_inode(sb, ino, &bh);
if (!raw_inode)
goto Eio;
} else
raw_inode++;
}
brelse(bh);
if (count != sb_count)
goto Einval;
out:
mutex_unlock(&sbi->s_lock);
return count;
Einval:
printk("sysv_count_free_inodes: "
"free inode count was %d, correcting to %d\n",
sb_count, count);
if (!sb_rdonly(sb)) {
*sbi->s_sb_total_free_inodes = cpu_to_fs16(SYSV_SB(sb), count);
dirty_sb(sb);
}
goto out;
Eio:
printk("sysv_count_free_inodes: unable to read inode table\n");
trust_sb:
count = sb_count;
goto out;
}