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-rw-r--r--Documentation/binfmt_misc.txt7
-rw-r--r--fs/binfmt_misc.c41
-rw-r--r--fs/internal.h1
-rw-r--r--fs/open.c20
4 files changed, 67 insertions, 2 deletions
diff --git a/Documentation/binfmt_misc.txt b/Documentation/binfmt_misc.txt
index 6b1de7058371..ec83bbce547a 100644
--- a/Documentation/binfmt_misc.txt
+++ b/Documentation/binfmt_misc.txt
@@ -66,6 +66,13 @@ Here is what the fields mean:
This feature should be used with care as the interpreter
will run with root permissions when a setuid binary owned by root
is run with binfmt_misc.
+ 'F' - fix binary. The usual behaviour of binfmt_misc is to spawn the
+ binary lazily when the misc format file is invoked. However,
+ this doesn't work very well in the face of mount namespaces and
+ changeroots, so the F mode opens the binary as soon as the
+ emulation is installed and uses the opened image to spawn the
+ emulator, meaning it is always available once installed,
+ regardless of how the environment changes.
There are some restrictions:
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 5417516f6e59..6103a6362ccd 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -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);
@@ -696,6 +718,21 @@ 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;
@@ -713,7 +750,7 @@ out:
if (err) {
kfree(e);
- return -EINVAL;
+ return err;
}
return count;
}
diff --git a/fs/internal.h b/fs/internal.h
index cc5a530e4f06..ba0737649d4a 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -111,6 +111,7 @@ extern long do_handle_open(int mountdirfd,
struct file_handle __user *ufh, int open_flag);
extern int open_check_o_direct(struct file *f);
extern int vfs_open(const struct path *, struct file *, const struct cred *);
+extern struct file *filp_clone_open(struct file *);
/*
* inode.c
diff --git a/fs/open.c b/fs/open.c
index bf66cf1a9f5c..4fd6e256f4f4 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -998,6 +998,26 @@ struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
}
EXPORT_SYMBOL(file_open_root);
+struct file *filp_clone_open(struct file *oldfile)
+{
+ struct file *file;
+ int retval;
+
+ file = get_empty_filp();
+ if (IS_ERR(file))
+ return file;
+
+ file->f_flags = oldfile->f_flags;
+ retval = vfs_open(&oldfile->f_path, file, oldfile->f_cred);
+ if (retval) {
+ put_filp(file);
+ return ERR_PTR(retval);
+ }
+
+ return file;
+}
+EXPORT_SYMBOL(filp_clone_open);
+
long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
{
struct open_flags op;