lkml.org 
[lkml]   [2015]   [Sep]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] fs: fix data race on mnt.mnt_flags
On Mon, Sep 21, 2015 at 02:16:47PM +0200, Dmitry Vyukov wrote:
> do_remount() does:
>
> mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
> mnt->mnt.mnt_flags = mnt_flags;
>
> This can easily be compiled as:
>
> mnt->mnt.mnt_flags &= ~MNT_USER_SETTABLE_MASK;
> mnt->mnt.mnt_flags |= mnt_flags;
>
> (also 2 memory accesses, less register pressure)
> The flags are being concurrently read by e.g. do_mmap_pgoff()
> which does:
>
> if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
>
> As the result we can allow to mmap a MNT_NOEXEC mount
> as VM_EXEC.
>
> Use WRITE_ONCE() to set new flags.
>
> The data race was found with KernelThreadSanitizer (KTSAN).
>
> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

--
Kirill A. Shutemov


\
 
 \ /
  Last update: 2015-09-21 16:21    [W:0.040 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site