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new helper: iterate_fd() 

iterates through the opened files in given descriptor table,
calling a supplied function; we stop once non-zero is returned.
Callback gets struct file *, descriptor number and const void *
argument passed to iterator.  It is called with files->file_lock
held, so it is not allowed to block.

tty_io, netprio_cgroup and selinux flush_unauthorized_files()
converted to its use.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
hifive-unleashed-5.1
Al Viro 2012-08-21 22:32:06 -04:00
parent ad47bd7252
commit c3c073f808
5 changed files with 71 additions and 84 deletions
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36
drivers/tty/tty_io.c
View File

@ -2791,6 +2791,13 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd,
}
#endif
static int this_tty(const void *t, struct file *file, unsigned fd)
{
if (likely(file->f_op->read != tty_read))
return 0;
return file_tty(file) != t ? 0 : fd + 1;
}
/*
* This implements the "Secure Attention Key" --- the idea is to
* prevent trojan horses by killing all processes associated with this
@ -2818,8 +2825,6 @@ void __do_SAK(struct tty_struct *tty)
struct task_struct *g, *p;
struct pid *session;
int i;
struct file *filp;
struct fdtable *fdt;
if (!tty)
return;
@ -2849,27 +2854,12 @@ void __do_SAK(struct tty_struct *tty)
continue;
}
task_lock(p);
if (p->files) {
/*
* We don't take a ref to the file, so we must
* hold ->file_lock instead.
*/
spin_lock(&p->files->file_lock);
fdt = files_fdtable(p->files);
for (i = 0; i < fdt->max_fds; i++) {
filp = fcheck_files(p->files, i);
if (!filp)
continue;
if (filp->f_op->read == tty_read &&
file_tty(filp) == tty) {
printk(KERN_NOTICE "SAK: killed process %d"
" (%s): fd#%d opened to the tty\n",
task_pid_nr(p), p->comm, i);
force_sig(SIGKILL, p);
break;
}
}
spin_unlock(&p->files->file_lock);
i = iterate_fd(p->files, 0, this_tty, tty);
if (i != 0) {
printk(KERN_NOTICE "SAK: killed process %d"
" (%s): fd#%d opened to the tty\n",
task_pid_nr(p), p->comm, i - 1);
force_sig(SIGKILL, p);
}
task_unlock(p);
} while_each_thread(g, p);

21
fs/file.c
View File

@ -979,3 +979,24 @@ int f_dupfd(unsigned int from, struct file *file, unsigned flags)
}
return err;
}
int iterate_fd(struct files_struct *files, unsigned n,
int (*f)(const void *, struct file *, unsigned),
const void *p)
{
struct fdtable *fdt;
struct file *file;
int res = 0;
if (!files)
return 0;
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
while (!res && n < fdt->max_fds) {
file = rcu_dereference_check_fdtable(files, fdt->fd[n++]);
if (file)
res = f(p, file, n);
}
spin_unlock(&files->file_lock);
return res;
}
EXPORT_SYMBOL(iterate_fd);

3
include/linux/fdtable.h
View File

@ -98,6 +98,9 @@ void reset_files_struct(struct files_struct *);
int unshare_files(struct files_struct **);
struct files_struct *dup_fd(struct files_struct *, int *);
void do_close_on_exec(struct files_struct *);
int iterate_fd(struct files_struct *, unsigned,
int (*)(const void *, struct file *, unsigned),
const void *);
extern int __alloc_fd(struct files_struct *files,
unsigned start, unsigned end, unsigned flags);

38
net/core/netprio_cgroup.c
View File

@ -272,38 +272,24 @@ out_free_devname:
return ret;
}
static int update_netprio(const void *v, struct file *file, unsigned n)
{
int err;
struct socket *sock = sock_from_file(file, &err);
if (sock)
sock->sk->sk_cgrp_prioidx = (u32)(unsigned long)v;
return 0;
}
void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
{
struct task_struct *p;
void *v;
cgroup_taskset_for_each(p, cgrp, tset) {
unsigned int fd;
struct fdtable *fdt;
struct files_struct *files;
task_lock(p);
files = p->files;
if (!files) {
task_unlock(p);
continue;
}
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
for (fd = 0; fd < fdt->max_fds; fd++) {
struct file *file;
struct socket *sock;
int err;
file = fcheck_files(files, fd);
if (!file)
continue;
sock = sock_from_file(file, &err);
if (sock)
sock_update_netprioidx(sock->sk, p);
}
spin_unlock(&files->file_lock);
v = (void *)(unsigned long)task_netprioidx(p);
iterate_fd(p->files, 0, update_netprio, v);
task_unlock(p);
}
}

57
security/selinux/hooks.c
View File

@ -2088,15 +2088,19 @@ static int selinux_bprm_secureexec(struct linux_binprm *bprm)
return (atsecure || cap_bprm_secureexec(bprm));
}
static int match_file(const void *p, struct file *file, unsigned fd)
{
return file_has_perm(p, file, file_to_av(file)) ? fd + 1 : 0;
}
/* Derived from fs/exec.c:flush_old_files. */
static inline void flush_unauthorized_files(const struct cred *cred,
struct files_struct *files)
{
struct file *file, *devnull = NULL;
struct tty_struct *tty;
struct fdtable *fdt;
long j = -1;
int drop_tty = 0;
unsigned n;
tty = get_current_tty();
if (tty) {
@ -2123,41 +2127,24 @@ static inline void flush_unauthorized_files(const struct cred *cred,
no_tty();
/* Revalidate access to inherited open files. */
spin_lock(&files->file_lock);
for (;;) {
unsigned long set, i;
j++;
i = j * BITS_PER_LONG;
fdt = files_fdtable(files);
if (i >= fdt->max_fds)
break;
set = fdt->open_fds[j];
if (!set)
continue;
spin_unlock(&files->file_lock);
for ( ; set ; i++, set >>= 1) {
if (!(set & 1))
continue;
file = fget(i);
if (!file)
continue;
if (file_has_perm(cred, file, file_to_av(file))) {
if (devnull) {
get_file(devnull);
} else {
devnull = dentry_open(&selinux_null,
O_RDWR, cred);
if (IS_ERR(devnull))
devnull = NULL;
}
replace_fd(i, devnull, 0);
}
fput(file);
}
spin_lock(&files->file_lock);
n = iterate_fd(files, 0, match_file, cred);
if (!n) /* none found? */
return;
devnull = dentry_open(&selinux_null, O_RDWR, cred);
if (!IS_ERR(devnull)) {
/* replace all the matching ones with this */
do {
get_file(devnull);
replace_fd(n - 1, devnull, 0);
} while ((n = iterate_fd(files, n, match_file, cred)) != 0);
fput(devnull);
} else {
/* just close all the matching ones */
do {
replace_fd(n - 1, NULL, 0);
} while ((n = iterate_fd(files, n, match_file, cred)) != 0);
}
spin_unlock(&files->file_lock);
}
/*