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c/r: prctl: less paranoid prctl_set_mm_exe_file()

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"no other files mapped" requirement from my previous patch (c/r: prctl:
update prctl_set_mm_exe_file() after mm->num_exe_file_vmas removal) is too
paranoid, it forbids operation even if there mapped one shared-anon vma.

Let's check that current mm->exe_file already unmapped, in this case
exe_file symlink already outdated and its changing is reasonable.

Plus, this patch fixes exit code in case operation success.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Reported-by: Cyrill Gorcunov <gorcunov@openvz.org>
Tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Konstantin Khlebnikov 2012-07-11 14:02:11 -07:00 committed by Linus Torvalds
parent a4e08d001f
commit 4229fb1dc6
1 changed files with 10 additions and 6 deletions
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16
kernel/sys.c
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@ -1788,7 +1788,6 @@ SYSCALL_DEFINE1(umask, int, mask)
#ifdef CONFIG_CHECKPOINT_RESTORE
static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
{
struct vm_area_struct *vma;
struct file *exe_file;
struct dentry *dentry;
int err;
@ -1816,13 +1815,17 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
down_write(&mm->mmap_sem);
/*
* Forbid mm->exe_file change if there are mapped other files.
* Forbid mm->exe_file change if old file still mapped.
*/
err = -EBUSY;
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (vma->vm_file && !path_equal(&vma->vm_file->f_path,
&exe_file->f_path))
goto exit_unlock;
if (mm->exe_file) {
struct vm_area_struct *vma;
for (vma = mm->mmap; vma; vma = vma->vm_next)
if (vma->vm_file &&
path_equal(&vma->vm_file->f_path,
&mm->exe_file->f_path))
goto exit_unlock;
}
/*
@ -1835,6 +1838,7 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
if (test_and_set_bit(MMF_EXE_FILE_CHANGED, &mm->flags))
goto exit_unlock;
err = 0;
set_mm_exe_file(mm, exe_file);
exit_unlock:
up_write(&mm->mmap_sem);