From e320d3012d25b1fb5f3df4edb7bd44a1c362ec10 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Tue, 13 Oct 2020 16:56:04 -0700 Subject: mm/page_alloc.c: fix freeing non-compound pages Here is a very rare race which leaks memory: Page P0 is allocated to the page cache. Page P1 is free. Thread A Thread B Thread C find_get_entry(): xas_load() returns P0 Removes P0 from page cache P0 finds its buddy P1 alloc_pages(GFP_KERNEL, 1) returns P0 P0 has refcount 1 page_cache_get_speculative(P0) P0 has refcount 2 __free_pages(P0) P0 has refcount 1 put_page(P0) P1 is not freed Fix this by freeing all the pages in __free_pages() that won't be freed by the call to put_page(). It's usually not a good idea to split a page, but this is a very unlikely scenario. Fixes: e286781d5f2e ("mm: speculative page references") Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton Acked-by: Mike Rapoport Cc: Nick Piggin Cc: Hugh Dickins Cc: Peter Zijlstra Link: https://lkml.kernel.org/r/20200926213919.26642-1-willy@infradead.org Signed-off-by: Linus Torvalds --- lib/Makefile | 1 + 1 file changed, 1 insertion(+) (limited to 'lib/Makefile') diff --git a/lib/Makefile b/lib/Makefile index d4af75136c54..49a2a9e36224 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -101,6 +101,7 @@ obj-$(CONFIG_TEST_BLACKHOLE_DEV) += test_blackhole_dev.o obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o obj-$(CONFIG_TEST_LOCKUP) += test_lockup.o obj-$(CONFIG_TEST_HMM) += test_hmm.o +obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o # # CFLAGS for compiling floating point code inside the kernel. x86/Makefile turns -- cgit