Messages in this thread |  | | | Date | Fri, 2 Mar 2012 16:26:22 +0100 | | From | Oleg Nesterov <> | | Subject | Re: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file |
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On 03/02, Cyrill Gorcunov wrote: > > On Thu, Mar 01, 2012 at 08:41:20PM +0100, Oleg Nesterov wrote: > ... > > Still can't understand. I think you need: > > > > file = fget(fd); > > if (!file) > > return -EBADF; > > > > down_write(&mm->mmap_sem); > > if (mm->num_exe_file_vmas) { > > fput(mm->exe_file); > > mm->exe_file = file; > > file = NULL; > > } > > up_write(&mm->mmap_sem); > > > > if (!file) > > return 0; > > > > fput(file); > > return -ESOMETHING; > > > > and that is all. > > Hi Oleg, sure you were right. I even think testing for > num_exe_file_vmas is not needed, since until real > executable VMA is read and mapped it might remain > zero. So I guess something like below should work.
No, you need to check num_exe_file_vmas != 0.
> +static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd) > +{ > + struct file *new_exe_file, *old_exe_file; > + > + new_exe_file = fget(fd); > + if (!new_exe_file) > + return -EBADF; > + > + down_write(&mm->mmap_sem); > + old_exe_file = mm->exe_file; > + mm->exe_file = new_exe_file; > + up_write(&mm->mmap_sem);
This changes the current rule: mm->exe_file goes away once num_exe_file_vmas becomes zero.
Oleg.
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