The patch titled
Subject: c/r: prctl: add ability to set new mm_struct::exe_file
has been added to the -mm tree. Its filename is
c-r-prctl-add-ability-to-set-new-mm_struct-exe_file.patch
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------------------------------------------------------
From: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Subject: c/r: prctl: add ability to set new mm_struct::exe_file
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 option takes a
file descriptor which will be set as a source for new /proc/$pid/exe
symlink.
Note it allows to change /proc/$pid/exe iif there are no VM_EXECUTABLE
vmas present for current process, simply because this feature is a special
to C/R and mm::num_exe_file_vmas become meaningless after that.
Also this action is one-shot only. For security reason we don't allow to
change the symlink several times.
This feature is available iif CONFIG_CHECKPOINT_RESTORE is set.
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Matt Helsley <matthltc@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/prctl.h | 1
kernel/sys.c | 56 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)
diff -puN include/linux/prctl.h~c-r-prctl-add-ability-to-set-new-mm_struct-exe_file include/linux/prctl.h
--- a/include/linux/prctl.h~c-r-prctl-add-ability-to-set-new-mm_struct-exe_file
+++ a/include/linux/prctl.h
@@ -118,6 +118,7 @@
# 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
/*
* Set specific pid that is allowed to ptrace the current task.
diff -puN kernel/sys.c~c-r-prctl-add-ability-to-set-new-mm_struct-exe_file kernel/sys.c
--- a/kernel/sys.c~c-r-prctl-add-ability-to-set-new-mm_struct-exe_file
+++ a/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>
@@ -1710,6 +1712,57 @@ 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;
+
+ /*
+ * Setting new mm::exe_file is only allowed
+ * when no VM_EXECUTABLE vma's left. So make
+ * a fast test first.
+ */
+ if (mm->num_exe_file_vmas)
+ return -EBUSY;
+
+ exe_file = fget(fd);
+ if (!exe_file)
+ return -EBADF;
+
+ dentry = exe_file->f_path.dentry;
+
+ /*
+ * Because the original mm->exe_file
+ * points to executable file, make sure
+ * this one is executable as well to not
+ * break an overall picture.
+ */
+ err = -EACCES;
+ if (!S_ISREG(dentry->d_inode->i_mode) ||
+ exe_file->f_path.mnt->mnt_flags & MNT_NOEXEC)
+ goto exit;
+
+ err = inode_permission(dentry->d_inode, MAY_EXEC);
+ if (err)
+ goto exit;
+
+ /*
+ * For security reason changing mm->exe_file
+ * is one-shot action.
+ */
+ down_write(&mm->mmap_sem);
+ if (likely(!mm->exe_file))
+ set_mm_exe_file(mm, exe_file);
+ else
+ err = -EBUSY;
+ up_write(&mm->mmap_sem);
+
+exit:
+ fput(exe_file);
+ return err;
+}
+
static int prctl_set_mm(int opt, unsigned long addr,
unsigned long arg4, unsigned long arg5)
{
@@ -1724,6 +1777,9 @@ static int prctl_set_mm(int opt, unsigne
if (!capable(CAP_SYS_RESOURCE))
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;
_
Subject: Subject: c/r: prctl: add ability to set new mm_struct::exe_file
Patches currently in -mm which might be from gorcunov@xxxxxxxxxx are
linux-next.patch
sysctl-make-kernelns_last_pid-control-being-checkpoint_restore-dependent.patch
fs-proc-introduce-proc-pid-task-tid-children-entry-v9.patch
syscalls-x86-add-__nr_kcmp-syscall-v8.patch
syscalls-x86-add-__nr_kcmp-syscall-v8-fix.patch
syscalls-x86-add-__nr_kcmp-syscall-v8-fix-2.patch
c-r-procfs-add-arg_start-end-env_start-end-and-exit_code-members-to-proc-pid-stat.patch
c-r-prctl-extend-pr_set_mm-to-set-up-more-mm_struct-entries-v2.patch
c-r-prctl-add-ability-to-set-new-mm_struct-exe_file.patch
c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-fix.patch
c-r-prctl-add-ability-to-get-clear_tid_address.patch
c-r-prctl-add-ability-to-get-clear_tid_address-fix.patch
--
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