--- /dev/null
+From 3d36424b3b5850bd92f3e89b953a430d7cfc88ef Mon Sep 17 00:00:00 2001
+From: Mel Gorman <mgorman@techsingularity.net>
+Date: Wed, 24 Aug 2022 12:14:50 +0100
+Subject: mm/page_alloc: fix race condition between build_all_zonelists and page allocation
+
+From: Mel Gorman <mgorman@techsingularity.net>
+
+commit 3d36424b3b5850bd92f3e89b953a430d7cfc88ef upstream.
+
+Patrick Daly reported the following problem;
+
+ NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK] - before offline operation
+ [0] - ZONE_MOVABLE
+ [1] - ZONE_NORMAL
+ [2] - NULL
+
+ For a GFP_KERNEL allocation, alloc_pages_slowpath() will save the
+ offset of ZONE_NORMAL in ac->preferred_zoneref. If a concurrent
+ memory_offline operation removes the last page from ZONE_MOVABLE,
+ build_all_zonelists() & build_zonerefs_node() will update
+ node_zonelists as shown below. Only populated zones are added.
+
+ NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK] - after offline operation
+ [0] - ZONE_NORMAL
+ [1] - NULL
+ [2] - NULL
+
+The race is simple -- page allocation could be in progress when a memory
+hot-remove operation triggers a zonelist rebuild that removes zones. The
+allocation request will still have a valid ac->preferred_zoneref that is
+now pointing to NULL and triggers an OOM kill.
+
+This problem probably always existed but may be slightly easier to trigger
+due to 6aa303defb74 ("mm, vmscan: only allocate and reclaim from zones
+with pages managed by the buddy allocator") which distinguishes between
+zones that are completely unpopulated versus zones that have valid pages
+not managed by the buddy allocator (e.g. reserved, memblock, ballooning
+etc). Memory hotplug had multiple stages with timing considerations
+around managed/present page updates, the zonelist rebuild and the zone
+span updates. As David Hildenbrand puts it
+
+ memory offlining adjusts managed+present pages of the zone
+ essentially in one go. If after the adjustments, the zone is no
+ longer populated (present==0), we rebuild the zone lists.
+
+ Once that's done, we try shrinking the zone (start+spanned
+ pages) -- which results in zone_start_pfn == 0 if there are no
+ more pages. That happens *after* rebuilding the zonelists via
+ remove_pfn_range_from_zone().
+
+The only requirement to fix the race is that a page allocation request
+identifies when a zonelist rebuild has happened since the allocation
+request started and no page has yet been allocated. Use a seqlock_t to
+track zonelist updates with a lockless read-side of the zonelist and
+protecting the rebuild and update of the counter with a spinlock.
+
+[akpm@linux-foundation.org: make zonelist_update_seq static]
+Link: https://lkml.kernel.org/r/20220824110900.vh674ltxmzb3proq@techsingularity.net
+Fixes: 6aa303defb74 ("mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator")
+Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
+Reported-by: Patrick Daly <quic_pdaly@quicinc.com>
+Acked-by: Michal Hocko <mhocko@suse.com>
+Reviewed-by: David Hildenbrand <david@redhat.com>
+Cc: <stable@vger.kernel.org> [4.9+]
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ mm/page_alloc.c | 53 +++++++++++++++++++++++++++++++++++++++++++----------
+ 1 file changed, 43 insertions(+), 10 deletions(-)
+
+--- a/mm/page_alloc.c
++++ b/mm/page_alloc.c
+@@ -3567,6 +3567,30 @@ void fs_reclaim_release(gfp_t gfp_mask)
+ EXPORT_SYMBOL_GPL(fs_reclaim_release);
+ #endif
+
++/*
++ * Zonelists may change due to hotplug during allocation. Detect when zonelists
++ * have been rebuilt so allocation retries. Reader side does not lock and
++ * retries the allocation if zonelist changes. Writer side is protected by the
++ * embedded spin_lock.
++ */
++static DEFINE_SEQLOCK(zonelist_update_seq);
++
++static unsigned int zonelist_iter_begin(void)
++{
++ if (IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
++ return read_seqbegin(&zonelist_update_seq);
++
++ return 0;
++}
++
++static unsigned int check_retry_zonelist(unsigned int seq)
++{
++ if (IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
++ return read_seqretry(&zonelist_update_seq, seq);
++
++ return seq;
++}
++
+ /* Perform direct synchronous page reclaim */
+ static int
+ __perform_reclaim(gfp_t gfp_mask, unsigned int order,
+@@ -3870,6 +3894,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, u
+ int compaction_retries;
+ int no_progress_loops;
+ unsigned int cpuset_mems_cookie;
++ unsigned int zonelist_iter_cookie;
+ int reserve_flags;
+
+ /*
+@@ -3880,11 +3905,12 @@ __alloc_pages_slowpath(gfp_t gfp_mask, u
+ (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
+ gfp_mask &= ~__GFP_ATOMIC;
+
+-retry_cpuset:
++restart:
+ compaction_retries = 0;
+ no_progress_loops = 0;
+ compact_priority = DEF_COMPACT_PRIORITY;
+ cpuset_mems_cookie = read_mems_allowed_begin();
++ zonelist_iter_cookie = zonelist_iter_begin();
+
+ /*
+ * The fast path uses conservative alloc_flags to succeed only until
+@@ -4032,9 +4058,13 @@ retry:
+ goto retry;
+
+
+- /* Deal with possible cpuset update races before we start OOM killing */
+- if (check_retry_cpuset(cpuset_mems_cookie, ac))
+- goto retry_cpuset;
++ /*
++ * Deal with possible cpuset update races or zonelist updates to avoid
++ * a unnecessary OOM kill.
++ */
++ if (check_retry_cpuset(cpuset_mems_cookie, ac) ||
++ check_retry_zonelist(zonelist_iter_cookie))
++ goto restart;
+
+ /* Reclaim has failed us, start killing things */
+ page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
+@@ -4054,9 +4084,13 @@ retry:
+ }
+
+ nopage:
+- /* Deal with possible cpuset update races before we fail */
+- if (check_retry_cpuset(cpuset_mems_cookie, ac))
+- goto retry_cpuset;
++ /*
++ * Deal with possible cpuset update races or zonelist updates to avoid
++ * a unnecessary OOM kill.
++ */
++ if (check_retry_cpuset(cpuset_mems_cookie, ac) ||
++ check_retry_zonelist(zonelist_iter_cookie))
++ goto restart;
+
+ /*
+ * Make sure that __GFP_NOFAIL request doesn't leak out and make sure
+@@ -5167,9 +5201,8 @@ static void __build_all_zonelists(void *
+ int nid;
+ int __maybe_unused cpu;
+ pg_data_t *self = data;
+- static DEFINE_SPINLOCK(lock);
+
+- spin_lock(&lock);
++ write_seqlock(&zonelist_update_seq);
+
+ #ifdef CONFIG_NUMA
+ memset(node_load, 0, sizeof(node_load));
+@@ -5202,7 +5235,7 @@ static void __build_all_zonelists(void *
+ #endif
+ }
+
+- spin_unlock(&lock);
++ write_sequnlock(&zonelist_update_seq);
+ }
+
+ static noinline void __init
--- /dev/null
+From dac22531bbd4af2426c4e29e05594415ccfa365d Mon Sep 17 00:00:00 2001
+From: Maurizio Lombardi <mlombard@redhat.com>
+Date: Fri, 15 Jul 2022 14:50:13 +0200
+Subject: mm: prevent page_frag_alloc() from corrupting the memory
+
+From: Maurizio Lombardi <mlombard@redhat.com>
+
+commit dac22531bbd4af2426c4e29e05594415ccfa365d upstream.
+
+A number of drivers call page_frag_alloc() with a fragment's size >
+PAGE_SIZE.
+
+In low memory conditions, __page_frag_cache_refill() may fail the order
+3 cache allocation and fall back to order 0; In this case, the cache
+will be smaller than the fragment, causing memory corruptions.
+
+Prevent this from happening by checking if the newly allocated cache is
+large enough for the fragment; if not, the allocation will fail and
+page_frag_alloc() will return NULL.
+
+Link: https://lkml.kernel.org/r/20220715125013.247085-1-mlombard@redhat.com
+Fixes: b63ae8ca096d ("mm/net: Rename and move page fragment handling from net/ to mm/")
+Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
+Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
+Cc: Chen Lin <chen45464546@163.com>
+Cc: Jakub Kicinski <kuba@kernel.org>
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ mm/page_alloc.c | 12 ++++++++++++
+ 1 file changed, 12 insertions(+)
+
+--- a/mm/page_alloc.c
++++ b/mm/page_alloc.c
+@@ -4391,6 +4391,18 @@ refill:
+ /* reset page count bias and offset to start of new frag */
+ nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
+ offset = size - fragsz;
++ if (unlikely(offset < 0)) {
++ /*
++ * The caller is trying to allocate a fragment
++ * with fragsz > PAGE_SIZE but the cache isn't big
++ * enough to satisfy the request, this may
++ * happen in low memory conditions.
++ * We don't release the cache page because
++ * it could make memory pressure worse
++ * so we simply return NULL here.
++ */
++ return NULL;
++ }
+ }
+
+ nc->pagecnt_bias--;
projects / thirdparty / kernel / stable-queue.git / commitdiff
