| Message ID | 20240306212749.1823380-1-willy@infradead.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: Fix list corruption in put_pages_list | expand |
On Wed, 6 Mar 2024 21:27:30 +0000 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote: > My recent change to put_pages_list() dereferences folio->lru.next after > returning the folio to the page allocator. Usually this is now on the > pcp list with other free folios, so we try to free an already-free > folio. This only happens with lists that have more than 15 entries, so > it wasn't immediately discovered. Revert to using list_for_each_safe() > so we dereference lru.next before disposing of the folio. > > Reported-by: "Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com> I'm unable to find the bug report on linux-mm. Help please? > Fixes: 24835f899c01 (mm: use free_unref_folios() in put_pages_list()) > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > --- > mm/swap.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index a910af21ba68..1d4b7713605d 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -139,10 +139,10 @@ EXPORT_SYMBOL(__folio_put); > void put_pages_list(struct list_head *pages) > { > struct folio_batch fbatch; > - struct folio *folio; > + struct folio *folio, *next; > > folio_batch_init(&fbatch); > - list_for_each_entry(folio, pages, lru) { > + list_for_each_entry_safe(folio, next, pages, lru) { > if (!folio_put_testzero(folio)) > continue; > if (folio_test_hugetlb(folio)) { > -- > 2.43.0
On Wed, Mar 06, 2024 at 01:45:57PM -0800, Andrew Morton wrote: > On Wed, 6 Mar 2024 21:27:30 +0000 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote: > > > My recent change to put_pages_list() dereferences folio->lru.next after > > returning the folio to the page allocator. Usually this is now on the > > pcp list with other free folios, so we try to free an already-free > > folio. This only happens with lists that have more than 15 entries, so > > it wasn't immediately discovered. Revert to using list_for_each_safe() > > so we dereference lru.next before disposing of the folio. > > > > Reported-by: "Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com> > > I'm unable to find the bug report on linux-mm. Help please? https://lore.kernel.org/intel-gfx/SJ1PR11MB61292145F3B79DA58ADDDA63B9232@SJ1PR11MB6129.namprd11.prod.outlook.com/ (wasn't cc'd to linux-mm)
On Wed, 6 Mar 2024 21:47:35 +0000 Matthew Wilcox <willy@infradead.org> wrote: > On Wed, Mar 06, 2024 at 01:45:57PM -0800, Andrew Morton wrote: > > On Wed, 6 Mar 2024 21:27:30 +0000 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote: > > > > > My recent change to put_pages_list() dereferences folio->lru.next after > > > returning the folio to the page allocator. Usually this is now on the > > > pcp list with other free folios, so we try to free an already-free > > > folio. This only happens with lists that have more than 15 entries, so > > > it wasn't immediately discovered. Revert to using list_for_each_safe() > > > so we dereference lru.next before disposing of the folio. > > > > > > Reported-by: "Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com> > > > > I'm unable to find the bug report on linux-mm. Help please? > > https://lore.kernel.org/intel-gfx/SJ1PR11MB61292145F3B79DA58ADDDA63B9232@SJ1PR11MB6129.namprd11.prod.outlook.com/ > > (wasn't cc'd to linux-mm) Ah, OK, thanks. I'll add that as a Closes: thingy.
diff --git a/mm/swap.c b/mm/swap.c index a910af21ba68..1d4b7713605d 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -139,10 +139,10 @@ EXPORT_SYMBOL(__folio_put); void put_pages_list(struct list_head *pages) { struct folio_batch fbatch; - struct folio *folio; + struct folio *folio, *next; folio_batch_init(&fbatch); - list_for_each_entry(folio, pages, lru) { + list_for_each_entry_safe(folio, next, pages, lru) { if (!folio_put_testzero(folio)) continue; if (folio_test_hugetlb(folio)) {
My recent change to put_pages_list() dereferences folio->lru.next after returning the folio to the page allocator. Usually this is now on the pcp list with other free folios, so we try to free an already-free folio. This only happens with lists that have more than 15 entries, so it wasn't immediately discovered. Revert to using list_for_each_safe() so we dereference lru.next before disposing of the folio. Reported-by: "Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com> Fixes: 24835f899c01 (mm: use free_unref_folios() in put_pages_list()) Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- mm/swap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)