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new helper: iterate_fd()

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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>
This commit is contained in:
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
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@@ -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);