| Message ID | 161044409809.1482714.11965583624142790079.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: Fix pfn_to_online_page() with respect to ZONE_DEVICE | expand |
On Tue, Jan 12, 2021 at 01:34:58AM -0800, Dan Williams wrote: > The conversion to move pfn_to_online_page() internal to > soft_offline_page() missed that the get_user_pages() reference needs to > be dropped when pfn_to_online_page() fails. I would be more specific here wrt. get_user_pages (madvise). soft_offline_page gets called from more places besides madvise_*. > When soft_offline_page() is handed a pfn_valid() && > !pfn_to_online_page() pfn the kernel hangs at dax-device shutdown due to > a leaked reference. > > Fixes: feec24a6139d ("mm, soft-offline: convert parameter to pfn") > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Oscar Salvador <osalvador@suse.de> > Cc: <stable@vger.kernel.org> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> LGTM, thanks for catching this: Reviewed-by: Oscar Salvador <osalvador@suse.de> A nit below. > --- > mm/memory-failure.c | 20 ++++++++++++++++---- > 1 file changed, 16 insertions(+), 4 deletions(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 5a38e9eade94..78b173c7190c 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1885,6 +1885,12 @@ static int soft_offline_free_page(struct page *page) > return rc; > } > > +static void put_ref_page(struct page *page) > +{ > + if (page) > + put_page(page); > +} I am not sure this warrants a function. I would probably go with "if (ref_page).." in the two corresponding places, but not feeling strong here. > + > /** > * soft_offline_page - Soft offline a page. > * @pfn: pfn to soft-offline > @@ -1910,20 +1916,26 @@ static int soft_offline_free_page(struct page *page) > int soft_offline_page(unsigned long pfn, int flags) > { > int ret; > - struct page *page; > bool try_again = true; > + struct page *page, *ref_page = NULL; > + > + WARN_ON_ONCE(!pfn_valid(pfn) && (flags & MF_COUNT_INCREASED)); Did you see any scenario where this could happen? I understand that you are adding this because we will leak a reference in case pfn is not valid anymore.
On 12.01.21 10:34, Dan Williams wrote: > The conversion to move pfn_to_online_page() internal to > soft_offline_page() missed that the get_user_pages() reference needs to > be dropped when pfn_to_online_page() fails. > > When soft_offline_page() is handed a pfn_valid() && > !pfn_to_online_page() pfn the kernel hangs at dax-device shutdown due to > a leaked reference. > > Fixes: feec24a6139d ("mm, soft-offline: convert parameter to pfn") > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Oscar Salvador <osalvador@suse.de> > Cc: <stable@vger.kernel.org> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > --- > mm/memory-failure.c | 20 ++++++++++++++++---- > 1 file changed, 16 insertions(+), 4 deletions(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 5a38e9eade94..78b173c7190c 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1885,6 +1885,12 @@ static int soft_offline_free_page(struct page *page) > return rc; > } > > +static void put_ref_page(struct page *page) > +{ > + if (page) > + put_page(page); > +} > + > /** > * soft_offline_page - Soft offline a page. > * @pfn: pfn to soft-offline > @@ -1910,20 +1916,26 @@ static int soft_offline_free_page(struct page *page) > int soft_offline_page(unsigned long pfn, int flags) > { > int ret; > - struct page *page; > bool try_again = true; > + struct page *page, *ref_page = NULL; > + > + WARN_ON_ONCE(!pfn_valid(pfn) && (flags & MF_COUNT_INCREASED)); > > if (!pfn_valid(pfn)) > return -ENXIO; > + if (flags & MF_COUNT_INCREASED) > + ref_page = pfn_to_page(pfn); > + > /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */ > page = pfn_to_online_page(pfn); > - if (!page) > + if (!page) { > + put_ref_page(ref_page); > return -EIO; > + } > > if (PageHWPoison(page)) { > pr_info("%s: %#lx page already poisoned\n", __func__, pfn); > - if (flags & MF_COUNT_INCREASED) > - put_page(page); > + put_ref_page(ref_page); > return 0; > } Reviewed-by: David Hildenbrand <david@redhat.com>
On Tue, Jan 12, 2021 at 1:54 AM Oscar Salvador <osalvador@suse.de> wrote: > > On Tue, Jan 12, 2021 at 01:34:58AM -0800, Dan Williams wrote: > > The conversion to move pfn_to_online_page() internal to > > soft_offline_page() missed that the get_user_pages() reference needs to > > be dropped when pfn_to_online_page() fails. > > I would be more specific here wrt. get_user_pages (madvise). > soft_offline_page gets called from more places besides madvise_*. Sure. > > > When soft_offline_page() is handed a pfn_valid() && > > !pfn_to_online_page() pfn the kernel hangs at dax-device shutdown due to > > a leaked reference. > > > > Fixes: feec24a6139d ("mm, soft-offline: convert parameter to pfn") > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> > > Cc: David Hildenbrand <david@redhat.com> > > Cc: Michal Hocko <mhocko@kernel.org> > > Cc: Oscar Salvador <osalvador@suse.de> > > Cc: <stable@vger.kernel.org> > > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > > LGTM, thanks for catching this: > > Reviewed-by: Oscar Salvador <osalvador@suse.de> > > A nit below. > > > --- > > mm/memory-failure.c | 20 ++++++++++++++++---- > > 1 file changed, 16 insertions(+), 4 deletions(-) > > > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > > index 5a38e9eade94..78b173c7190c 100644 > > --- a/mm/memory-failure.c > > +++ b/mm/memory-failure.c > > @@ -1885,6 +1885,12 @@ static int soft_offline_free_page(struct page *page) > > return rc; > > } > > > > +static void put_ref_page(struct page *page) > > +{ > > + if (page) > > + put_page(page); > > +} > > I am not sure this warrants a function. > I would probably go with "if (ref_page).." in the two corresponding places, > but not feeling strong here. I'll take another look, it felt cluttered... > > > + > > /** > > * soft_offline_page - Soft offline a page. > > * @pfn: pfn to soft-offline > > @@ -1910,20 +1916,26 @@ static int soft_offline_free_page(struct page *page) > > int soft_offline_page(unsigned long pfn, int flags) > > { > > int ret; > > - struct page *page; > > bool try_again = true; > > + struct page *page, *ref_page = NULL; > > + > > + WARN_ON_ONCE(!pfn_valid(pfn) && (flags & MF_COUNT_INCREASED)); > > Did you see any scenario where this could happen? I understand that you are > adding this because we will leak a reference in case pfn is not valid anymore. > I did not, more future proofing / documenting against refactoring that fails to consider that case.
diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 5a38e9eade94..78b173c7190c 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1885,6 +1885,12 @@ static int soft_offline_free_page(struct page *page) return rc; } +static void put_ref_page(struct page *page) +{ + if (page) + put_page(page); +} + /** * soft_offline_page - Soft offline a page. * @pfn: pfn to soft-offline @@ -1910,20 +1916,26 @@ static int soft_offline_free_page(struct page *page) int soft_offline_page(unsigned long pfn, int flags) { int ret; - struct page *page; bool try_again = true; + struct page *page, *ref_page = NULL; + + WARN_ON_ONCE(!pfn_valid(pfn) && (flags & MF_COUNT_INCREASED)); if (!pfn_valid(pfn)) return -ENXIO; + if (flags & MF_COUNT_INCREASED) + ref_page = pfn_to_page(pfn); + /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */ page = pfn_to_online_page(pfn); - if (!page) + if (!page) { + put_ref_page(ref_page); return -EIO; + } if (PageHWPoison(page)) { pr_info("%s: %#lx page already poisoned\n", __func__, pfn); - if (flags & MF_COUNT_INCREASED) - put_page(page); + put_ref_page(ref_page); return 0; }
The conversion to move pfn_to_online_page() internal to soft_offline_page() missed that the get_user_pages() reference needs to be dropped when pfn_to_online_page() fails. When soft_offline_page() is handed a pfn_valid() && !pfn_to_online_page() pfn the kernel hangs at dax-device shutdown due to a leaked reference. Fixes: feec24a6139d ("mm, soft-offline: convert parameter to pfn") Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Cc: David Hildenbrand <david@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: <stable@vger.kernel.org> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- mm/memory-failure.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)