Messages in this thread | | | Date | Fri, 9 Mar 2012 13:48:11 +0100 | From | Oleg Nesterov <> | Subject | Re: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file v3 |
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On 03/09, Cyrill Gorcunov wrote: > > +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; > + > + /* > + * 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; > + > + /* > + * Setting new mm::exe_file is only allowed > + * when no executable VMAs left. This is ^^^^^^^^^^ Perhaps this is just me, but imho "executable" is not clear enough. I'd suggest VM_EXECUTABLE to avoid the confusion with VM_EXEC.
> + * special C/R case when a restored program > + * need to change own /proc/$pid/exe symlink. > + * After this call mm::num_exe_file_vmas become > + * meaningless. > + */ > + down_write(&mm->mmap_sem); > + if (mm->num_exe_file_vmas == 0) {
You can check this at the very start lockless and simplify the code. Once it is zero, it can never grow (or we have a bug anyway).
> + set_mm_exe_file(mm, exe_file); > + exe_file = NULL; > + } else > + err = -EBUSY; > + up_write(&mm->mmap_sem); > + > +exit: > + if (exe_file) > + fput(exe_file);
This doesn't look correct, you need fput() in any case. set_mm_exe_file() does another get_file().
Oleg.
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