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afs: Implement @sys substitution handling 

Implement the AFS feature by which @sys at the end of a pathname component
may be substituted for one of a list of values, typically naming the
operating system.  Up to 16 alternatives may be specified and these are
tried in turn until one works.  Each network namespace has[*] a separate
independent list.

Upon creation of a new network namespace, the list of values is
initialised[*] to a single OpenAFS-compatible string representing arch type
plus "_linux26".  For example, on x86_64, the sysname is "amd64_linux26".

[*] Or will, once network namespace support is finalised in kAFS.

The list may be set by:

	# for i in foo bar linux-x86_64; do echo $i; done >/proc/fs/afs/sysname

for which separate writes to the same fd are amalgamated and applied on
close.  The LF character may be used as a separator to specify multiple
items in the same write() call.

The list may be cleared by:

	# echo >/proc/fs/afs/sysname

and read by:

	# cat /proc/fs/afs/sysname
	foo
	bar
	linux-x86_64

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2018-04-09 21:12:31 +01:00
parent 5cf9dd55a0
commit 6f8880d8e6
5 changed files with 380 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
Documentation/filesystems/afs.txt
View File

@ -11,7 +11,7 @@ Contents:
- Proc filesystem.
- The cell database.
- Security.
- Examples.
- The @sys substitution.
========
@ -230,3 +230,29 @@ If a file is opened with a particular key and then the file descriptor is
passed to a process that doesn't have that key (perhaps over an AF_UNIX
socket), then the operations on the file will be made with key that was used to
open the file.
=====================
THE @SYS SUBSTITUTION
=====================
The list of up to 16 @sys substitutions for the current network namespace can
be configured by writing a list to /proc/fs/afs/sysname:
[root@andromeda ~]# echo foo amd64_linux_26 >/proc/fs/afs/sysname
or cleared entirely by writing an empty list:
[root@andromeda ~]# echo >/proc/fs/afs/sysname
The current list for current network namespace can be retrieved by:
[root@andromeda ~]# cat /proc/fs/afs/sysname
foo
amd64_linux_26
When @sys is being substituted for, each element of the list is tried in the
order given.
By default, the list will contain one item that conforms to the pattern
"<arch>_linux_26", amd64 being the name for x86_64.

63
fs/afs/dir.c
View File

@ -766,6 +766,62 @@ out:
return ERR_PTR(ret);
}
/*
* Look up an entry in a directory with @sys substitution.
*/
static struct dentry *afs_lookup_atsys(struct inode *dir, struct dentry *dentry,
struct key *key)
{
struct afs_sysnames *subs;
struct afs_net *net = afs_i2net(dir);
struct dentry *ret;
char *buf, *p, *name;
int len, i;
_enter("");
ret = ERR_PTR(-ENOMEM);
p = buf = kmalloc(AFSNAMEMAX, GFP_KERNEL);
if (!buf)
goto out_p;
if (dentry->d_name.len > 4) {
memcpy(p, dentry->d_name.name, dentry->d_name.len - 4);
p += dentry->d_name.len - 4;
}
/* There is an ordered list of substitutes that we have to try. */
read_lock(&net->sysnames_lock);
subs = net->sysnames;
refcount_inc(&subs->usage);
read_unlock(&net->sysnames_lock);
for (i = 0; i < subs->nr; i++) {
name = subs->subs[i];
len = dentry->d_name.len - 4 + strlen(name);
if (len >= AFSNAMEMAX) {
ret = ERR_PTR(-ENAMETOOLONG);
goto out_s;
}
strcpy(p, name);
ret = lookup_one_len(buf, dentry->d_parent, len);
if (IS_ERR(ret) || d_is_positive(ret))
goto out_s;
dput(ret);
}
/* We don't want to d_add() the @sys dentry here as we don't want to
* the cached dentry to hide changes to the sysnames list.
*/
ret = NULL;
out_s:
afs_put_sysnames(subs);
kfree(buf);
out_p:
key_put(key);
return ret;
}
/*
* look up an entry in a directory
*/
@ -805,6 +861,13 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
return ERR_PTR(ret);
}
if (dentry->d_name.len >= 4 &&
dentry->d_name.name[dentry->d_name.len - 4] == '@' &&
dentry->d_name.name[dentry->d_name.len - 3] == 's' &&
dentry->d_name.name[dentry->d_name.len - 2] == 'y' &&
dentry->d_name.name[dentry->d_name.len - 1] == 's')
return afs_lookup_atsys(dir, dentry, key);
inode = afs_do_lookup(dir, dentry, key);
if (IS_ERR(inode)) {
ret = PTR_ERR(inode);

16
fs/afs/internal.h
View File

@ -198,6 +198,18 @@ static inline struct afs_super_info *AFS_FS_S(struct super_block *sb)
extern struct file_system_type afs_fs_type;
/*
* Set of substitutes for @sys.
*/
struct afs_sysnames {
#define AFS_NR_SYSNAME 16
char *subs[AFS_NR_SYSNAME];
refcount_t usage;
unsigned short nr;
short error;
char blank[1];
};
/*
* AFS network namespace record.
*/
@ -246,8 +258,11 @@ struct afs_net {
/* Misc */
struct proc_dir_entry *proc_afs; /* /proc/net/afs directory */
struct afs_sysnames *sysnames;
rwlock_t sysnames_lock;
};
extern const char afs_init_sysname[];
extern struct afs_net __afs_net;// Dummy AFS network namespace; TODO: replace with real netns
enum afs_cell_state {
@ -789,6 +804,7 @@ extern int __net_init afs_proc_init(struct afs_net *);
extern void __net_exit afs_proc_cleanup(struct afs_net *);
extern int afs_proc_cell_setup(struct afs_net *, struct afs_cell *);
extern void afs_proc_cell_remove(struct afs_net *, struct afs_cell *);
extern void afs_put_sysnames(struct afs_sysnames *);
/*
* rotate.c

44
fs/afs/main.c
View File

@ -34,11 +34,42 @@ MODULE_PARM_DESC(rootcell, "root AFS cell name and VL server IP addr list");
struct workqueue_struct *afs_wq;
struct afs_net __afs_net;
#if defined(CONFIG_ALPHA)
const char afs_init_sysname[] = "alpha_linux26";
#elif defined(CONFIG_X86_64)
const char afs_init_sysname[] = "amd64_linux26";
#elif defined(CONFIG_ARM)
const char afs_init_sysname[] = "arm_linux26";
#elif defined(CONFIG_ARM64)
const char afs_init_sysname[] = "aarch64_linux26";
#elif defined(CONFIG_X86_32)
const char afs_init_sysname[] = "i386_linux26";
#elif defined(CONFIG_IA64)
const char afs_init_sysname[] = "ia64_linux26";
#elif defined(CONFIG_PPC64)
const char afs_init_sysname[] = "ppc64_linux26";
#elif defined(CONFIG_PPC32)
const char afs_init_sysname[] = "ppc_linux26";
#elif defined(CONFIG_S390)
#ifdef CONFIG_64BIT
const char afs_init_sysname[] = "s390x_linux26";
#else
const char afs_init_sysname[] = "s390_linux26";
#endif
#elif defined(CONFIG_SPARC64)
const char afs_init_sysname[] = "sparc64_linux26";
#elif defined(CONFIG_SPARC32)
const char afs_init_sysname[] = "sparc_linux26";
#else
const char afs_init_sysname[] = "unknown_linux26";
#endif
/*
* Initialise an AFS network namespace record.
*/
static int __net_init afs_net_init(struct afs_net *net)
{
struct afs_sysnames *sysnames;
int ret;
net->live = true;
@ -67,6 +98,16 @@ static int __net_init afs_net_init(struct afs_net *net)
INIT_WORK(&net->fs_manager, afs_manage_servers);
timer_setup(&net->fs_timer, afs_servers_timer, 0);
ret = -ENOMEM;
sysnames = kzalloc(sizeof(*sysnames), GFP_KERNEL);
if (!sysnames)
goto error_sysnames;
sysnames->subs[0] = (char *)&afs_init_sysname;
sysnames->nr = 1;
refcount_set(&sysnames->usage, 1);
net->sysnames = sysnames;
rwlock_init(&net->sysnames_lock);
/* Register the /proc stuff */
ret = afs_proc_init(net);
if (ret < 0)
@ -92,6 +133,8 @@ error_cell_init:
net->live = false;
afs_proc_cleanup(net);
error_proc:
afs_put_sysnames(net->sysnames);
error_sysnames:
net->live = false;
return ret;
}
@ -106,6 +149,7 @@ static void __net_exit afs_net_exit(struct afs_net *net)
afs_purge_servers(net);
afs_close_socket(net);
afs_proc_cleanup(net);
afs_put_sysnames(net->sysnames);
}
/*

231
fs/afs/proc.c
View File

@ -126,6 +126,32 @@ static const struct file_operations afs_proc_servers_fops = {
.release = seq_release,
};
static int afs_proc_sysname_open(struct inode *inode, struct file *file);
static int afs_proc_sysname_release(struct inode *inode, struct file *file);
static void *afs_proc_sysname_start(struct seq_file *p, loff_t *pos);
static void *afs_proc_sysname_next(struct seq_file *p, void *v,
loff_t *pos);
static void afs_proc_sysname_stop(struct seq_file *p, void *v);
static int afs_proc_sysname_show(struct seq_file *m, void *v);
static ssize_t afs_proc_sysname_write(struct file *file,
const char __user *buf,
size_t size, loff_t *_pos);
static const struct seq_operations afs_proc_sysname_ops = {
.start = afs_proc_sysname_start,
.next = afs_proc_sysname_next,
.stop = afs_proc_sysname_stop,
.show = afs_proc_sysname_show,
};
static const struct file_operations afs_proc_sysname_fops = {
.open = afs_proc_sysname_open,
.read = seq_read,
.llseek = seq_lseek,
.release = afs_proc_sysname_release,
.write = afs_proc_sysname_write,
};
/*
* initialise the /proc/fs/afs/ directory
*/
@ -139,7 +165,8 @@ int afs_proc_init(struct afs_net *net)
if (!proc_create("cells", 0644, net->proc_afs, &afs_proc_cells_fops) ||
!proc_create("rootcell", 0644, net->proc_afs, &afs_proc_rootcell_fops) ||
!proc_create("servers", 0644, net->proc_afs, &afs_proc_servers_fops))
!proc_create("servers", 0644, net->proc_afs, &afs_proc_servers_fops) ||
!proc_create("sysname", 0644, net->proc_afs, &afs_proc_sysname_fops))
goto error_tree;
_leave(" = 0");
@ -330,6 +357,12 @@ static ssize_t afs_proc_rootcell_write(struct file *file,
if (IS_ERR(kbuf))
return PTR_ERR(kbuf);
ret = -EINVAL;
if (kbuf[0] == '.')
goto out;
if (memchr(kbuf, '/', size))
goto out;
/* trim to first NL */
s = memchr(kbuf, '\n', size);
if (s)
@ -342,6 +375,7 @@ static ssize_t afs_proc_rootcell_write(struct file *file,
if (ret >= 0)
ret = size; /* consume everything, always */
out:
kfree(kbuf);
_leave(" = %d", ret);
return ret;
@ -635,3 +669,198 @@ static int afs_proc_servers_show(struct seq_file *m, void *v)
&alist->addrs[alist->index].transport);
return 0;
}
void afs_put_sysnames(struct afs_sysnames *sysnames)
{
int i;
if (sysnames && refcount_dec_and_test(&sysnames->usage)) {
for (i = 0; i < sysnames->nr; i++)
if (sysnames->subs[i] != afs_init_sysname &&
sysnames->subs[i] != sysnames->blank)
kfree(sysnames->subs[i]);
}
}
/*
* Handle opening of /proc/fs/afs/sysname. If it is opened for writing, we
* assume the caller wants to change the substitution list and we allocate a
* buffer to hold the list.
*/
static int afs_proc_sysname_open(struct inode *inode, struct file *file)
{
struct afs_sysnames *sysnames;
struct seq_file *m;
int ret;
ret = seq_open(file, &afs_proc_sysname_ops);
if (ret < 0)
return ret;
if (file->f_mode & FMODE_WRITE) {
sysnames = kzalloc(sizeof(*sysnames), GFP_KERNEL);
if (!sysnames) {
seq_release(inode, file);
return -ENOMEM;
}
refcount_set(&sysnames->usage, 1);
m = file->private_data;
m->private = sysnames;
}
return 0;
}
/*
* Handle writes to /proc/fs/afs/sysname to set the @sys substitution.
*/
static ssize_t afs_proc_sysname_write(struct file *file,
const char __user *buf,
size_t size, loff_t *_pos)
{
struct afs_sysnames *sysnames;
struct seq_file *m = file->private_data;
char *kbuf = NULL, *s, *p, *sub;
int ret, len;
sysnames = m->private;
if (!sysnames)
return -EINVAL;
if (sysnames->error)
return sysnames->error;
if (size >= PAGE_SIZE - 1) {
sysnames->error = -EINVAL;
return -EINVAL;
}
if (size == 0)
return 0;
kbuf = memdup_user_nul(buf, size);
if (IS_ERR(kbuf))
return PTR_ERR(kbuf);
inode_lock(file_inode(file));
p = kbuf;
while ((s = strsep(&p, " \t\n"))) {
len = strlen(s);
if (len == 0)
continue;
ret = -ENAMETOOLONG;
if (len >= AFSNAMEMAX)
goto error;
if (len >= 4 &&
s[len - 4] == '@' &&
s[len - 3] == 's' &&
s[len - 2] == 'y' &&
s[len - 1] == 's')
/* Protect against recursion */
goto invalid;
if (s[0] == '.' &&
(len < 2 || (len == 2 && s[1] == '.')))
goto invalid;
if (memchr(s, '/', len))
goto invalid;
ret = -EFBIG;
if (sysnames->nr >= AFS_NR_SYSNAME)
goto out;
if (strcmp(s, afs_init_sysname) == 0) {
sub = (char *)afs_init_sysname;
} else {
ret = -ENOMEM;
sub = kmemdup(s, len + 1, GFP_KERNEL);
if (!sub)
goto out;
}
sysnames->subs[sysnames->nr] = sub;
sysnames->nr++;
}
ret = size; /* consume everything, always */
out:
inode_unlock(file_inode(file));
kfree(kbuf);
return ret;
invalid:
ret = -EINVAL;
error:
sysnames->error = ret;
goto out;
}
static int afs_proc_sysname_release(struct inode *inode, struct file *file)
{
struct afs_sysnames *sysnames, *kill = NULL;
struct seq_file *m = file->private_data;
struct afs_net *net = afs_seq2net(m);
sysnames = m->private;
if (sysnames) {
if (!sysnames->error) {
kill = sysnames;
if (sysnames->nr == 0) {
sysnames->subs[0] = sysnames->blank;
sysnames->nr++;
}
write_lock(&net->sysnames_lock);
kill = net->sysnames;
net->sysnames = sysnames;
write_unlock(&net->sysnames_lock);
}
afs_put_sysnames(kill);
}
return seq_release(inode, file);
}
static void *afs_proc_sysname_start(struct seq_file *m, loff_t *pos)
__acquires(&net->sysnames_lock)
{
struct afs_net *net = afs_seq2net(m);
struct afs_sysnames *names = net->sysnames;
read_lock(&net->sysnames_lock);
if (*pos >= names->nr)
return NULL;
return (void *)(unsigned long)(*pos + 1);
}
static void *afs_proc_sysname_next(struct seq_file *m, void *v, loff_t *pos)
{
struct afs_net *net = afs_seq2net(m);
struct afs_sysnames *names = net->sysnames;
*pos += 1;
if (*pos >= names->nr)
return NULL;
return (void *)(unsigned long)(*pos + 1);
}
static void afs_proc_sysname_stop(struct seq_file *m, void *v)
__releases(&net->sysnames_lock)
{
struct afs_net *net = afs_seq2net(m);
read_unlock(&net->sysnames_lock);
}
static int afs_proc_sysname_show(struct seq_file *m, void *v)
{
struct afs_net *net = afs_seq2net(m);
struct afs_sysnames *sysnames = net->sysnames;
unsigned int i = (unsigned long)v - 1;
if (i < sysnames->nr)
seq_printf(m, "%s\n", sysnames->subs[i]);
return 0;
}