Commit 948b701a authored by James Bottomley's avatar James Bottomley

binfmt_misc: add persistent opened binary handler for containers

This patch adds a new flag 'F' to the binfmt handlers.  If you pass in
'F' the binary that runs the emulation will be opened immediately and
in future, will be cloned from the open file.

The net effect is that the handler survives both changeroots and mount
namespace changes, making it easy to work with foreign architecture
containers without contaminating the container image with the
emulator.
Signed-off-by: 's avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
Acked-by: 's avatarSerge Hallyn <serge.hallyn@canonical.com>
parent 9a08c352
......@@ -26,6 +26,8 @@
#include <linux/fs.h>
#include <linux/uaccess.h>
#include "internal.h"
#ifdef DEBUG
# define USE_DEBUG 1
#else
......@@ -43,6 +45,7 @@ enum {Enabled, Magic};
#define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
#define MISC_FMT_OPEN_BINARY (1 << 30)
#define MISC_FMT_CREDENTIALS (1 << 29)
#define MISC_FMT_OPEN_FILE (1 << 28)
typedef struct {
struct list_head list;
......@@ -54,6 +57,7 @@ typedef struct {
char *interpreter; /* filename of interpreter */
char *name;
struct dentry *dentry;
struct file *interp_file;
} Node;
static DEFINE_RWLOCK(entries_lock);
......@@ -201,7 +205,13 @@ static int load_misc_binary(struct linux_binprm *bprm)
if (retval < 0)
goto error;
interp_file = open_exec(iname);
if (fmt->flags & MISC_FMT_OPEN_FILE && fmt->interp_file) {
interp_file = filp_clone_open(fmt->interp_file);
if (!IS_ERR(interp_file))
deny_write_access(interp_file);
} else {
interp_file = open_exec(iname);
}
retval = PTR_ERR(interp_file);
if (IS_ERR(interp_file))
goto error;
......@@ -285,6 +295,11 @@ static char *check_special_flags(char *sfs, Node *e)
e->flags |= (MISC_FMT_CREDENTIALS |
MISC_FMT_OPEN_BINARY);
break;
case 'F':
pr_debug("register: flag: F: open interpreter file now\n");
p++;
e->flags |= MISC_FMT_OPEN_FILE;
break;
default:
cont = 0;
}
......@@ -543,6 +558,8 @@ static void entry_status(Node *e, char *page)
*dp++ = 'O';
if (e->flags & MISC_FMT_CREDENTIALS)
*dp++ = 'C';
if (e->flags & MISC_FMT_OPEN_FILE)
*dp++ = 'F';
*dp++ = '\n';
if (!test_bit(Magic, &e->flags)) {
......@@ -590,6 +607,11 @@ static void kill_node(Node *e)
}
write_unlock(&entries_lock);
if ((e->flags & MISC_FMT_OPEN_FILE) && e->interp_file) {
filp_close(e->interp_file, NULL);
e->interp_file = NULL;
}
if (dentry) {
drop_nlink(d_inode(dentry));
d_drop(dentry);
......@@ -698,6 +720,21 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
goto out2;
}
if (e->flags & MISC_FMT_OPEN_FILE) {
struct file *f;
f = open_exec(e->interpreter);
if (IS_ERR(f)) {
err = PTR_ERR(f);
pr_notice("register: failed to install interpreter file %s\n", e->interpreter);
simple_release_fs(&bm_mnt, &entry_count);
iput(inode);
inode = NULL;
goto out2;
}
e->interp_file = f;
}
e->dentry = dget(dentry);
inode->i_private = e;
inode->i_fop = &bm_entry_operations;
......@@ -716,7 +753,7 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
if (err) {
kfree(e);
return -EINVAL;
return err;
}
return count;
}
......
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