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authorJames Bottomley <James.Bottomley@HansenPartnership.com>2016-02-17 16:51:16 -0800
committerJames Bottomley <James.Bottomley@HansenPartnership.com>2016-03-30 14:12:22 -0700
commit948b701a607f123df92ed29084413e5dd8cda2ed (patch)
treea8ec94afaa37da897e283923d20d3bde16897d97
parent9a08c352d05305ca7651540c3b107da1e4e1f40b (diff)
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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: James Bottomley <James.Bottomley@HansenPartnership.com> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
-rw-r--r--fs/binfmt_misc.c41
1 files changed, 39 insertions, 2 deletions
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 3a3ced779fc7..8a108c435bc6 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);
@@ -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 @@ out:
if (err) {
kfree(e);
- return -EINVAL;
+ return err;
}
return count;
}