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Message-ID: <20120303223333.GB26846@moon>
Date: Sun, 4 Mar 2012 02:33:33 +0400
From: Cyrill Gorcunov <gorcunov@...nvz.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Pavel Emelyanov <xemul@...allels.com>,
Kees Cook <keescook@...omium.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file
On Fri, Mar 02, 2012 at 08:12:47PM +0400, Cyrill Gorcunov wrote:
...
>
> Yes, Oleg, you're right of course! The set_mm_exe_file confused
> me a bit (I didn't reply to your previous emails simply because
> you were asking me to prove what exactly is broken when num_exe_file_vmas
> greater 2 and we reassign new exe_file, and I didn't know what to reply
> since I knew I was wrong in first assumption).
>
> As a conclusion -- sure I need to check for num_exe_file_vmas to
> not break current logic, thanks!
>
Hi Oleg,
i suppose the below one should do the trick. I mostly concerned
at moment if I added all permission tests needed.
Cyrill
---
c/r: prctl: Add ability to set new mm_struct::exe_file v2
From: Cyrill Gorcunov <gorcunov@...nvz.org>
When we do restore we would like to have a way to setup
a former mm_struct::exe_file so that /proc/pid/exe would
point to the original executable file a process had at
checkpoint time.
For this the PR_SET_MM_EXE_FILE code is introduced.
This feature is available iif CONFIG_CHECKPOINT_RESTORE is set.
Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
CC: Oleg Nesterov <oleg@...hat.com>
CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC: Pavel Emelyanov <xemul@...allels.com>
CC: Kees Cook <keescook@...omium.org>
CC: Tejun Heo <tj@...nel.org>
---
include/linux/prctl.h | 1
kernel/sys.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)
Index: linux-2.6.git/include/linux/prctl.h
===================================================================
--- linux-2.6.git.orig/include/linux/prctl.h
+++ linux-2.6.git/include/linux/prctl.h
@@ -118,5 +118,6 @@
# define PR_SET_MM_ENV_START 10
# define PR_SET_MM_ENV_END 11
# define PR_SET_MM_AUXV 12
+# define PR_SET_MM_EXE_FILE 13
#endif /* _LINUX_PRCTL_H */
Index: linux-2.6.git/kernel/sys.c
===================================================================
--- linux-2.6.git.orig/kernel/sys.c
+++ linux-2.6.git/kernel/sys.c
@@ -36,6 +36,8 @@
#include <linux/personality.h>
#include <linux/ptrace.h>
#include <linux/fs_struct.h>
+#include <linux/file.h>
+#include <linux/mount.h>
#include <linux/gfp.h>
#include <linux/syscore_ops.h>
#include <linux/version.h>
@@ -1701,6 +1703,56 @@ static bool vma_flags_mismatch(struct vm
(vma->vm_flags & banned);
}
+static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
+{
+ struct file *exe_file;
+ struct dentry *dentry;
+ int err;
+
+ exe_file = fget(fd);
+ if (!exe_file)
+ return -EBADF;
+
+ dentry = exe_file->f_path.dentry;
+
+ /*
+ * Permissions should be the same as if the
+ * file has being opened by the kernel for
+ * execution.
+ */
+ err = -EACCES;
+ if (!S_ISREG(dentry->d_inode->i_mode) ||
+ exe_file->f_path.mnt->mnt_flags & MNT_NOEXEC)
+ goto exit;
+
+ if ((exe_file->f_flags & O_ACCMODE) != O_RDONLY)
+ goto exit;
+
+ err = inode_permission(dentry->d_inode, MAY_EXEC);
+ if (err)
+ goto exit;
+
+ down_write(&mm->mmap_sem);
+ if (mm->num_exe_file_vmas) {
+
+ err = deny_write_access(exe_file);
+ if (err) {
+ up_write(&mm->mmap_sem);
+ goto exit;
+ }
+
+ fput(mm->exe_file);
+ mm->exe_file = exe_file;
+ } else {
+ fput(exe_file);
+ err = -ENXIO;
+ }
+ up_write(&mm->mmap_sem);
+
+exit:
+ return err;
+}
+
static int prctl_set_mm(int opt, unsigned long addr,
unsigned long arg4, unsigned long arg5)
{
@@ -1715,6 +1767,9 @@ static int prctl_set_mm(int opt, unsigne
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
+ if (opt == PR_SET_MM_EXE_FILE)
+ return prctl_set_mm_exe_file(mm, (unsigned int)addr);
+
if (addr >= TASK_SIZE)
return -EINVAL;
@@ -1837,6 +1892,7 @@ static int prctl_set_mm(int opt, unsigne
return 0;
}
+
default:
error = -EINVAL;
goto out;
--
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