linux/fs/autofs4/inode.c
Ian Kent a32744d4ab autofs: work around unhappy compat problem on x86-64
When the autofs protocol version 5 packet type was added in commit
5c0a32fc2c ("autofs4: add new packet type for v5 communications"), it
obvously tried quite hard to be word-size agnostic, and uses explicitly
sized fields that are all correctly aligned.

However, with the final "char name[NAME_MAX+1]" array at the end, the
actual size of the structure ends up being not very well defined:
because the struct isn't marked 'packed', doing a "sizeof()" on it will
align the size of the struct up to the biggest alignment of the members
it has.

And despite all the members being the same, the alignment of them is
different: a "__u64" has 4-byte alignment on x86-32, but native 8-byte
alignment on x86-64.  And while 'NAME_MAX+1' ends up being a nice round
number (256), the name[] array starts out a 4-byte aligned.

End result: the "packed" size of the structure is 300 bytes: 4-byte, but
not 8-byte aligned.

As a result, despite all the fields being in the same place on all
architectures, sizeof() will round up that size to 304 bytes on
architectures that have 8-byte alignment for u64.

Note that this is *not* a problem for 32-bit compat mode on POWER, since
there __u64 is 8-byte aligned even in 32-bit mode.  But on x86, 32-bit
and 64-bit alignment is different for 64-bit entities, and as a result
the structure that has exactly the same layout has different sizes.

So on x86-64, but no other architecture, we will just subtract 4 from
the size of the structure when running in a compat task.  That way we
will write the properly sized packet that user mode expects.

Not pretty.  Sadly, this very subtle, and unnecessary, size difference
has been encoded in user space that wants to read packets of *exactly*
the right size, and will refuse to touch anything else.

Reported-and-tested-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-02-25 12:10:27 -08:00

356 lines
8.1 KiB
C

/* -*- c -*- --------------------------------------------------------------- *
*
* linux/fs/autofs/inode.c
*
* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
* Copyright 2005-2006 Ian Kent <raven@themaw.net>
*
* This file is part of the Linux kernel and is made available under
* the terms of the GNU General Public License, version 2, or at your
* option, any later version, incorporated herein by reference.
*
* ------------------------------------------------------------------------- */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/seq_file.h>
#include <linux/pagemap.h>
#include <linux/parser.h>
#include <linux/bitops.h>
#include <linux/magic.h>
#include <linux/compat.h>
#include "autofs_i.h"
#include <linux/module.h>
struct autofs_info *autofs4_new_ino(struct autofs_sb_info *sbi)
{
struct autofs_info *ino = kzalloc(sizeof(*ino), GFP_KERNEL);
if (ino) {
INIT_LIST_HEAD(&ino->active);
INIT_LIST_HEAD(&ino->expiring);
ino->last_used = jiffies;
ino->sbi = sbi;
}
return ino;
}
void autofs4_clean_ino(struct autofs_info *ino)
{
ino->uid = 0;
ino->gid = 0;
ino->last_used = jiffies;
}
void autofs4_free_ino(struct autofs_info *ino)
{
kfree(ino);
}
void autofs4_kill_sb(struct super_block *sb)
{
struct autofs_sb_info *sbi = autofs4_sbi(sb);
/*
* In the event of a failure in get_sb_nodev the superblock
* info is not present so nothing else has been setup, so
* just call kill_anon_super when we are called from
* deactivate_super.
*/
if (!sbi)
goto out_kill_sb;
/* Free wait queues, close pipe */
autofs4_catatonic_mode(sbi);
sb->s_fs_info = NULL;
kfree(sbi);
out_kill_sb:
DPRINTK("shutting down");
kill_litter_super(sb);
}
static int autofs4_show_options(struct seq_file *m, struct dentry *root)
{
struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
struct inode *root_inode = root->d_sb->s_root->d_inode;
if (!sbi)
return 0;
seq_printf(m, ",fd=%d", sbi->pipefd);
if (root_inode->i_uid != 0)
seq_printf(m, ",uid=%u", root_inode->i_uid);
if (root_inode->i_gid != 0)
seq_printf(m, ",gid=%u", root_inode->i_gid);
seq_printf(m, ",pgrp=%d", sbi->oz_pgrp);
seq_printf(m, ",timeout=%lu", sbi->exp_timeout/HZ);
seq_printf(m, ",minproto=%d", sbi->min_proto);
seq_printf(m, ",maxproto=%d", sbi->max_proto);
if (autofs_type_offset(sbi->type))
seq_printf(m, ",offset");
else if (autofs_type_direct(sbi->type))
seq_printf(m, ",direct");
else
seq_printf(m, ",indirect");
return 0;
}
static void autofs4_evict_inode(struct inode *inode)
{
end_writeback(inode);
kfree(inode->i_private);
}
static const struct super_operations autofs4_sops = {
.statfs = simple_statfs,
.show_options = autofs4_show_options,
.evict_inode = autofs4_evict_inode,
};
enum {Opt_err, Opt_fd, Opt_uid, Opt_gid, Opt_pgrp, Opt_minproto, Opt_maxproto,
Opt_indirect, Opt_direct, Opt_offset};
static const match_table_t tokens = {
{Opt_fd, "fd=%u"},
{Opt_uid, "uid=%u"},
{Opt_gid, "gid=%u"},
{Opt_pgrp, "pgrp=%u"},
{Opt_minproto, "minproto=%u"},
{Opt_maxproto, "maxproto=%u"},
{Opt_indirect, "indirect"},
{Opt_direct, "direct"},
{Opt_offset, "offset"},
{Opt_err, NULL}
};
static int parse_options(char *options, int *pipefd, uid_t *uid, gid_t *gid,
pid_t *pgrp, unsigned int *type, int *minproto, int *maxproto)
{
char *p;
substring_t args[MAX_OPT_ARGS];
int option;
*uid = current_uid();
*gid = current_gid();
*pgrp = task_pgrp_nr(current);
*minproto = AUTOFS_MIN_PROTO_VERSION;
*maxproto = AUTOFS_MAX_PROTO_VERSION;
*pipefd = -1;
if (!options)
return 1;
while ((p = strsep(&options, ",")) != NULL) {
int token;
if (!*p)
continue;
token = match_token(p, tokens, args);
switch (token) {
case Opt_fd:
if (match_int(args, pipefd))
return 1;
break;
case Opt_uid:
if (match_int(args, &option))
return 1;
*uid = option;
break;
case Opt_gid:
if (match_int(args, &option))
return 1;
*gid = option;
break;
case Opt_pgrp:
if (match_int(args, &option))
return 1;
*pgrp = option;
break;
case Opt_minproto:
if (match_int(args, &option))
return 1;
*minproto = option;
break;
case Opt_maxproto:
if (match_int(args, &option))
return 1;
*maxproto = option;
break;
case Opt_indirect:
set_autofs_type_indirect(type);
break;
case Opt_direct:
set_autofs_type_direct(type);
break;
case Opt_offset:
set_autofs_type_offset(type);
break;
default:
return 1;
}
}
return (*pipefd < 0);
}
int autofs4_fill_super(struct super_block *s, void *data, int silent)
{
struct inode * root_inode;
struct dentry * root;
struct file * pipe;
int pipefd;
struct autofs_sb_info *sbi;
struct autofs_info *ino;
sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
if (!sbi)
goto fail_unlock;
DPRINTK("starting up, sbi = %p",sbi);
s->s_fs_info = sbi;
sbi->magic = AUTOFS_SBI_MAGIC;
sbi->pipefd = -1;
sbi->pipe = NULL;
sbi->catatonic = 1;
sbi->exp_timeout = 0;
sbi->oz_pgrp = task_pgrp_nr(current);
sbi->sb = s;
sbi->version = 0;
sbi->sub_version = 0;
set_autofs_type_indirect(&sbi->type);
sbi->min_proto = 0;
sbi->max_proto = 0;
sbi->compat_daemon = is_compat_task();
mutex_init(&sbi->wq_mutex);
mutex_init(&sbi->pipe_mutex);
spin_lock_init(&sbi->fs_lock);
sbi->queues = NULL;
spin_lock_init(&sbi->lookup_lock);
INIT_LIST_HEAD(&sbi->active_list);
INIT_LIST_HEAD(&sbi->expiring_list);
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;
s->s_magic = AUTOFS_SUPER_MAGIC;
s->s_op = &autofs4_sops;
s->s_d_op = &autofs4_dentry_operations;
s->s_time_gran = 1;
/*
* Get the root inode and dentry, but defer checking for errors.
*/
ino = autofs4_new_ino(sbi);
if (!ino)
goto fail_free;
root_inode = autofs4_get_inode(s, S_IFDIR | 0755);
if (!root_inode)
goto fail_ino;
root = d_alloc_root(root_inode);
if (!root)
goto fail_iput;
pipe = NULL;
root->d_fsdata = ino;
/* Can this call block? */
if (parse_options(data, &pipefd, &root_inode->i_uid, &root_inode->i_gid,
&sbi->oz_pgrp, &sbi->type, &sbi->min_proto,
&sbi->max_proto)) {
printk("autofs: called with bogus options\n");
goto fail_dput;
}
if (autofs_type_trigger(sbi->type))
__managed_dentry_set_managed(root);
root_inode->i_fop = &autofs4_root_operations;
root_inode->i_op = &autofs4_dir_inode_operations;
/* Couldn't this be tested earlier? */
if (sbi->max_proto < AUTOFS_MIN_PROTO_VERSION ||
sbi->min_proto > AUTOFS_MAX_PROTO_VERSION) {
printk("autofs: kernel does not match daemon version "
"daemon (%d, %d) kernel (%d, %d)\n",
sbi->min_proto, sbi->max_proto,
AUTOFS_MIN_PROTO_VERSION, AUTOFS_MAX_PROTO_VERSION);
goto fail_dput;
}
/* Establish highest kernel protocol version */
if (sbi->max_proto > AUTOFS_MAX_PROTO_VERSION)
sbi->version = AUTOFS_MAX_PROTO_VERSION;
else
sbi->version = sbi->max_proto;
sbi->sub_version = AUTOFS_PROTO_SUBVERSION;
DPRINTK("pipe fd = %d, pgrp = %u", pipefd, sbi->oz_pgrp);
pipe = fget(pipefd);
if (!pipe) {
printk("autofs: could not open pipe file descriptor\n");
goto fail_dput;
}
if (!pipe->f_op || !pipe->f_op->write)
goto fail_fput;
sbi->pipe = pipe;
sbi->pipefd = pipefd;
sbi->catatonic = 0;
/*
* Success! Install the root dentry now to indicate completion.
*/
s->s_root = root;
return 0;
/*
* Failure ... clean up.
*/
fail_fput:
printk("autofs: pipe file descriptor does not contain proper ops\n");
fput(pipe);
/* fall through */
fail_dput:
dput(root);
goto fail_free;
fail_iput:
printk("autofs: get root dentry failed\n");
iput(root_inode);
fail_ino:
kfree(ino);
fail_free:
kfree(sbi);
s->s_fs_info = NULL;
fail_unlock:
return -EINVAL;
}
struct inode *autofs4_get_inode(struct super_block *sb, umode_t mode)
{
struct inode *inode = new_inode(sb);
if (inode == NULL)
return NULL;
inode->i_mode = mode;
if (sb->s_root) {
inode->i_uid = sb->s_root->d_inode->i_uid;
inode->i_gid = sb->s_root->d_inode->i_gid;
}
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_ino = get_next_ino();
if (S_ISDIR(mode)) {
set_nlink(inode, 2);
inode->i_op = &autofs4_dir_inode_operations;
inode->i_fop = &autofs4_dir_operations;
} else if (S_ISLNK(mode)) {
inode->i_op = &autofs4_symlink_inode_operations;
}
return inode;
}