| Message ID | 20210423054038.26696-1-jgross@suse.com |
|---|---|
| State | Accepted |
| Commit | 970655aa9b42461f8394e4457307005bdeee14d9 |
| Headers | show |
| Series | xen/gntdev: fix gntdev_mmap() error exit path | expand |
On 23.04.21 08:55, Luca Fancellu wrote: > > >> On 23 Apr 2021, at 06:40, Juergen Gross <jgross@suse.com> wrote: >> >> Commit d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert") >> introduced an error in gntdev_mmap(): in case the call of >> mmu_interval_notifier_insert_locked() fails the exit path should not >> call mmu_interval_notifier_remove(), as this might result in NULL >> dereferences. >> >> One reason for failure is e.g. a signal pending for the running >> process. >> >> Fixes: d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert") >> Cc: stable@vger.kernel.org >> Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> >> Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> >> Signed-off-by: Juergen Gross <jgross@suse.com> >> --- >> drivers/xen/gntdev.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c >> index f01d58c7a042..a3e7be96527d 100644 >> --- a/drivers/xen/gntdev.c >> +++ b/drivers/xen/gntdev.c >> @@ -1017,8 +1017,10 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma) >> err = mmu_interval_notifier_insert_locked( >> &map->notifier, vma->vm_mm, vma->vm_start, >> vma->vm_end - vma->vm_start, &gntdev_mmu_ops); >> - if (err) >> + if (err) { >> + map->vma = NULL; >> goto out_unlock_put; >> + } >> } >> mutex_unlock(&priv->lock); >> >> -- >> 2.26.2 >> >> > > Hi Juergen, > > I can see from the code that there is another path to out_unlock_put label some lines before: > > […] > vma->vm_private_data = map; > if (map->flags) { > if ((vma->vm_flags & VM_WRITE) && > (map->flags & GNTMAP_readonly)) > goto out_unlock_put; > } else { > map->flags = GNTMAP_host_map; > if (!(vma->vm_flags & VM_WRITE)) > map->flags |= GNTMAP_readonly; > } > […] > > Can be the case that use_ptemod is != 0 also for that path? map->vma will be NULL in this case, so there will be no problem resulting from that path. Juergen
On Fri, Apr 23, 2021 at 08:04:57AM +0100, Luca Fancellu wrote: > > On 23 Apr 2021, at 08:00, Juergen Gross <jgross@suse.com> wrote: > > On 23.04.21 08:55, Luca Fancellu wrote: > >>> On 23 Apr 2021, at 06:40, Juergen Gross <jgross@suse.com> wrote: > >>> > >>> Commit d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert") > >>> introduced an error in gntdev_mmap(): in case the call of > >>> mmu_interval_notifier_insert_locked() fails the exit path should not > >>> call mmu_interval_notifier_remove(), as this might result in NULL > >>> dereferences. > >>> > >>> One reason for failure is e.g. a signal pending for the running > >>> process. > >>> > >>> Fixes: d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert") > >>> Cc: stable@vger.kernel.org > >>> Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > >>> Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > >>> Signed-off-by: Juergen Gross <jgross@suse.com> (...) > Right, thanks, seems good to me. > > Reviewed-by: Luca Fancellu <luca.fancellu@arm.com> Can somebody ack this fix please? -- Best Regards, Marek Marczykowski-Górecki Invisible Things Lab
On 23.04.21 07:40, Juergen Gross wrote: > Commit d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert") > introduced an error in gntdev_mmap(): in case the call of > mmu_interval_notifier_insert_locked() fails the exit path should not > call mmu_interval_notifier_remove(), as this might result in NULL > dereferences. > > One reason for failure is e.g. a signal pending for the running > process. > > Fixes: d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert") > Cc: stable@vger.kernel.org > Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > Signed-off-by: Juergen Gross <jgross@suse.com> Pushed to xen/tip.git for-linus-5.13b Juergen
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index f01d58c7a042..a3e7be96527d 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -1017,8 +1017,10 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma) err = mmu_interval_notifier_insert_locked( &map->notifier, vma->vm_mm, vma->vm_start, vma->vm_end - vma->vm_start, &gntdev_mmu_ops); - if (err) + if (err) { + map->vma = NULL; goto out_unlock_put; + } } mutex_unlock(&priv->lock);
Commit d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert") introduced an error in gntdev_mmap(): in case the call of mmu_interval_notifier_insert_locked() fails the exit path should not call mmu_interval_notifier_remove(), as this might result in NULL dereferences. One reason for failure is e.g. a signal pending for the running process. Fixes: d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert") Cc: stable@vger.kernel.org Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Signed-off-by: Juergen Gross <jgross@suse.com> --- drivers/xen/gntdev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)