diff --git a/include/linux/sched.h b/include/linux/sched.h index cff94cd..4a41270 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -437,6 +437,7 @@ extern int get_dumpable(struct mm_struct *mm); /* leave room for more dump flags */ #define MMF_VM_MERGEABLE 16 /* KSM may merge identical pages */ #define MMF_VM_HUGEPAGE 17 /* set when VM_HUGEPAGE is set on vma */ +#define MMF_EXE_FILE_CHANGED 18 /* see prctl(PR_SET_MM_EXE_FILE) */ #define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK) diff --git a/kernel/sys.c b/kernel/sys.c index da660f3..b217069 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1714,17 +1714,11 @@ static bool vma_flags_mismatch(struct vm_area_struct *vma, 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; - /* - * Setting new mm::exe_file is only allowed when no VM_EXECUTABLE vma's - * remain. So perform a quick test first. - */ - if (mm->num_exe_file_vmas) - return -EBUSY; - exe_file = fget(fd); if (!exe_file) return -EBADF; @@ -1745,17 +1739,28 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd) if (err) goto exit; + down_write(&mm->mmap_sem); + /* + * Forbid mm->exe_file change if there are mapped some other files. + */ + err = -EEXIST; + 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 out_unlock; + } /* * The symlink can be changed only once, just to disallow arbitrary * transitions malicious software might bring in. This means one * could make a snapshot over all processes running and monitor * /proc/pid/exe changes to notice unusual activity if needed. */ - down_write(&mm->mmap_sem); - if (likely(!mm->exe_file)) - set_mm_exe_file(mm, exe_file); - else - err = -EBUSY; + err = -EBUSY; + if (test_and_set_bit(MMF_EXE_FILE_CHANGED, &mm->flags)) + goto out_unlock; + set_mm_exe_file(mm, exe_file); + err = 0; +out_unlock: up_write(&mm->mmap_sem); exit: