From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bedivere.hansenpartnership.com ([66.63.167.143]:35382 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933377AbcBYThx (ORCPT ); Thu, 25 Feb 2016 14:37:53 -0500 Message-ID: <1456429071.2377.5.camel@HansenPartnership.com> Subject: [Patch v2 2/3] binfmt_misc: add persistent opened binary handler for containers From: James Bottomley To: containers@lists.linux-foundation.org, linux-fsdevel Cc: Al Viro Date: Thu, 25 Feb 2016 11:37:51 -0800 In-Reply-To: <1456428890.2377.2.camel@HansenPartnership.com> References: <1456428890.2377.2.camel@HansenPartnership.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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 --- fs/binfmt_misc.c | 41 +++++++++++++++++++++++++++++++++++++++-- 1 file changed, 39 insertions(+), 2 deletions(-) diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index 3a3ced7..8a108c4 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -26,6 +26,8 @@ #include #include +#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; } -- 2.6.2