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Date: Tue, 24 May 2016 15:04:33 -0400
From: Tejun Heo <tj@...nel.org>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
Sasha Levin <sasha.levin@...cle.com>, ast@...nel.org,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Christoph Lameter <cl@...ux.com>,
Linux-MM layout <linux-mm@...ck.org>, marco.gra@...il.com
Subject: Re: bpf: use-after-free in array_map_alloc
Hello,
Alexei, can you please verify this patch? Map extension got rolled
into balance work so that there's no sync issues between the two async
operations.
Thanks.
Index: work/mm/percpu.c
===================================================================
--- work.orig/mm/percpu.c
+++ work/mm/percpu.c
@@ -112,7 +112,7 @@ struct pcpu_chunk {
int map_used; /* # of map entries used before the sentry */
int map_alloc; /* # of map entries allocated */
int *map; /* allocation map */
- struct work_struct map_extend_work;/* async ->map[] extension */
+ struct list_head map_extend_list;/* on pcpu_map_extend_chunks */
void *data; /* chunk data */
int first_free; /* no free below this */
@@ -162,10 +162,13 @@ static struct pcpu_chunk *pcpu_reserved_
static int pcpu_reserved_chunk_limit;
static DEFINE_SPINLOCK(pcpu_lock); /* all internal data structures */
-static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop */
+static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop, map ext */
static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
+/* chunks which need their map areas extended, protected by pcpu_lock */
+static LIST_HEAD(pcpu_map_extend_chunks);
+
/*
* The number of empty populated pages, protected by pcpu_lock. The
* reserved chunk doesn't contribute to the count.
@@ -395,13 +398,19 @@ static int pcpu_need_to_extend(struct pc
{
int margin, new_alloc;
+ lockdep_assert_held(&pcpu_lock);
+
if (is_atomic) {
margin = 3;
if (chunk->map_alloc <
- chunk->map_used + PCPU_ATOMIC_MAP_MARGIN_LOW &&
- pcpu_async_enabled)
- schedule_work(&chunk->map_extend_work);
+ chunk->map_used + PCPU_ATOMIC_MAP_MARGIN_LOW) {
+ if (list_empty(&chunk->map_extend_list)) {
+ list_add_tail(&chunk->map_extend_list,
+ &pcpu_map_extend_chunks);
+ pcpu_schedule_balance_work();
+ }
+ }
} else {
margin = PCPU_ATOMIC_MAP_MARGIN_HIGH;
}
@@ -435,6 +444,8 @@ static int pcpu_extend_area_map(struct p
size_t old_size = 0, new_size = new_alloc * sizeof(new[0]);
unsigned long flags;
+ lockdep_assert_held(&pcpu_alloc_mutex);
+
new = pcpu_mem_zalloc(new_size);
if (!new)
return -ENOMEM;
@@ -467,20 +478,6 @@ out_unlock:
return 0;
}
-static void pcpu_map_extend_workfn(struct work_struct *work)
-{
- struct pcpu_chunk *chunk = container_of(work, struct pcpu_chunk,
- map_extend_work);
- int new_alloc;
-
- spin_lock_irq(&pcpu_lock);
- new_alloc = pcpu_need_to_extend(chunk, false);
- spin_unlock_irq(&pcpu_lock);
-
- if (new_alloc)
- pcpu_extend_area_map(chunk, new_alloc);
-}
-
/**
* pcpu_fit_in_area - try to fit the requested allocation in a candidate area
* @chunk: chunk the candidate area belongs to
@@ -740,7 +737,7 @@ static struct pcpu_chunk *pcpu_alloc_chu
chunk->map_used = 1;
INIT_LIST_HEAD(&chunk->list);
- INIT_WORK(&chunk->map_extend_work, pcpu_map_extend_workfn);
+ INIT_LIST_HEAD(&chunk->map_extend_list);
chunk->free_size = pcpu_unit_size;
chunk->contig_hint = pcpu_unit_size;
@@ -895,6 +892,9 @@ static void __percpu *pcpu_alloc(size_t
return NULL;
}
+ if (!is_atomic)
+ mutex_lock(&pcpu_alloc_mutex);
+
spin_lock_irqsave(&pcpu_lock, flags);
/* serve reserved allocations from the reserved chunk if available */
@@ -967,12 +967,9 @@ restart:
if (is_atomic)
goto fail;
- mutex_lock(&pcpu_alloc_mutex);
-
if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) {
chunk = pcpu_create_chunk();
if (!chunk) {
- mutex_unlock(&pcpu_alloc_mutex);
err = "failed to allocate new chunk";
goto fail;
}
@@ -983,7 +980,6 @@ restart:
spin_lock_irqsave(&pcpu_lock, flags);
}
- mutex_unlock(&pcpu_alloc_mutex);
goto restart;
area_found:
@@ -993,8 +989,6 @@ area_found:
if (!is_atomic) {
int page_start, page_end, rs, re;
- mutex_lock(&pcpu_alloc_mutex);
-
page_start = PFN_DOWN(off);
page_end = PFN_UP(off + size);
@@ -1005,7 +999,6 @@ area_found:
spin_lock_irqsave(&pcpu_lock, flags);
if (ret) {
- mutex_unlock(&pcpu_alloc_mutex);
pcpu_free_area(chunk, off, &occ_pages);
err = "failed to populate";
goto fail_unlock;
@@ -1045,6 +1038,8 @@ fail:
/* see the flag handling in pcpu_blance_workfn() */
pcpu_atomic_alloc_failed = true;
pcpu_schedule_balance_work();
+ } else {
+ mutex_unlock(&pcpu_alloc_mutex);
}
return NULL;
}
@@ -1129,6 +1124,7 @@ static void pcpu_balance_workfn(struct w
if (chunk == list_first_entry(free_head, struct pcpu_chunk, list))
continue;
+ list_del_init(&chunk->map_extend_list);
list_move(&chunk->list, &to_free);
}
@@ -1146,6 +1142,24 @@ static void pcpu_balance_workfn(struct w
pcpu_destroy_chunk(chunk);
}
+ do {
+ int new_alloc = 0;
+
+ spin_lock_irq(&pcpu_lock);
+
+ chunk = list_first_entry_or_null(&pcpu_map_extend_chunks,
+ struct pcpu_chunk, map_extend_list);
+ if (chunk) {
+ list_del_init(&chunk->map_extend_list);
+ new_alloc = pcpu_need_to_extend(chunk, false);
+ }
+
+ spin_unlock_irq(&pcpu_lock);
+
+ if (new_alloc)
+ pcpu_extend_area_map(chunk, new_alloc);
+ } while (chunk);
+
/*
* Ensure there are certain number of free populated pages for
* atomic allocs. Fill up from the most packed so that atomic
@@ -1644,7 +1658,7 @@ int __init pcpu_setup_first_chunk(const
*/
schunk = memblock_virt_alloc(pcpu_chunk_struct_size, 0);
INIT_LIST_HEAD(&schunk->list);
- INIT_WORK(&schunk->map_extend_work, pcpu_map_extend_workfn);
+ INIT_LIST_HEAD(&schunk->map_extend_list);
schunk->base_addr = base_addr;
schunk->map = smap;
schunk->map_alloc = ARRAY_SIZE(smap);
@@ -1673,7 +1687,7 @@ int __init pcpu_setup_first_chunk(const
if (dyn_size) {
dchunk = memblock_virt_alloc(pcpu_chunk_struct_size, 0);
INIT_LIST_HEAD(&dchunk->list);
- INIT_WORK(&dchunk->map_extend_work, pcpu_map_extend_workfn);
+ INIT_LIST_HEAD(&dchunk->map_extend_list);
dchunk->base_addr = base_addr;
dchunk->map = dmap;
dchunk->map_alloc = ARRAY_SIZE(dmap);
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