kernel-fxtec-pro1x/fs/autofs4/inode.c
Linus Torvalds 64f371bc31 autofs: make the autofsv5 packet file descriptor use a packetized pipe
The autofs packet size has had a very unfortunate size problem on x86:
because the alignment of 'u64' differs in 32-bit and 64-bit modes, and
because the packet data was not 8-byte aligned, the size of the autofsv5
packet structure differed between 32-bit and 64-bit modes despite
looking otherwise identical (300 vs 304 bytes respectively).

We first fixed that up by making the 64-bit compat mode know about this
problem in commit a32744d4ab ("autofs: work around unhappy compat
problem on x86-64"), and that made a 32-bit 'systemd' work happily on a
64-bit kernel because everything then worked the same way as on a 32-bit
kernel.

But it turned out that 'automount' had actually known and worked around
this problem in user space, so fixing the kernel to do the proper 32-bit
compatibility handling actually *broke* 32-bit automount on a 64-bit
kernel, because it knew that the packet sizes were wrong and expected
those incorrect sizes.

As a result, we ended up reverting that compatibility mode fix, and
thus breaking systemd again, in commit fcbf94b9de.

With both automount and systemd doing a single read() system call, and
verifying that they get *exactly* the size they expect but using
different sizes, it seemed that fixing one of them inevitably seemed to
break the other.  At one point, a patch I seriously considered applying
from Michael Tokarev did a "strcmp()" to see if it was automount that
was doing the operation.  Ugly, ugly.

However, a prettier solution exists now thanks to the packetized pipe
mode.  By marking the communication pipe as being packetized (by simply
setting the O_DIRECT flag), we can always just write the bigger packet
size, and if user-space does a smaller read, it will just get that
partial end result and the extra alignment padding will simply be thrown
away.

This makes both automount and systemd happy, since they now get the size
they asked for, and the kernel side of autofs simply no longer needs to
care - it could pad out the packet arbitrarily.

Of course, if there is some *other* user of autofs (please, please,
please tell me it ain't so - and we haven't heard of any) that tries to
read the packets with multiple writes, that other user will now be
broken - the whole point of the packetized mode is that one system call
gets exactly one packet, and you cannot read a packet in pieces.

Tested-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Miller <davem@davemloft.net>
Cc: Ian Kent <raven@themaw.net>
Cc: Thomas Meyer <thomas@m3y3r.de>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-04-29 13:30:08 -07:00

348 lines
8 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 "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;
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);
root = d_make_root(root_inode);
if (!root)
goto fail_ino;
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 (autofs_prepare_pipe(pipe) < 0)
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_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;
}