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percpu: Fix synchronization with chunk destruction (CVE-2016-4794)

This commit is contained in:
Ben Hutchings 2016-06-25 00:11:57 +02:00
parent b782c52536
commit f5f99415a2
4 changed files with 263 additions and 0 deletions
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4
debian/changelog vendored
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@ -5,6 +5,10 @@ linux (4.6.2-2) UNRELEASED; urgency=medium
- mm/memcontrol: mem_cgroup_migrate() - replace another local_irq_disable()
w. local_lock_irq()
* KEYS: potential uninitialized variable (CVE-2016-4470)
* percpu: fix synchronization between chunk->map_extend_work and chunk
destruction (CVE-2016-4794)
* percpu: fix synchronization between synchronous map extension and
chunk destruction (CVE-2016-4794)
-- Ben Hutchings <ben@decadent.org.uk> Thu, 16 Jun 2016 12:37:27 +0100

153
debian/patches/bugfix/all/percpu-fix-synchronization-between-chunk-map_extend_.patch vendored Normal file
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@ -0,0 +1,153 @@
From: Tejun Heo <tj@kernel.org>
Date: Wed, 25 May 2016 11:48:25 -0400
Subject: percpu: fix synchronization between chunk->map_extend_work and chunk
destruction
Origin: https://git.kernel.org/linus/4f996e234dad488e5d9ba0858bc1bae12eff82c3
Atomic allocations can trigger async map extensions which is serviced
by chunk->map_extend_work. pcpu_balance_work which is responsible for
destroying idle chunks wasn't synchronizing properly against
chunk->map_extend_work and may end up freeing the chunk while the work
item is still in flight.
This patch fixes the bug by rolling async map extension operations
into pcpu_balance_work.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: stable@vger.kernel.org # v3.18+
Fixes: 9c824b6a172c ("percpu: make sure chunk->map array has available space")
---
mm/percpu.c | 57 ++++++++++++++++++++++++++++++++++++---------------------
1 file changed, 36 insertions(+), 21 deletions(-)
diff --git a/mm/percpu.c b/mm/percpu.c
index 0c59684f1ff2..b1d2a3844792 100644
--- a/mm/percpu.c
+++ b/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 */
@@ -166,6 +166,9 @@ static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop */
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 pcpu_chunk *chunk, bool is_atomic)
{
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;
}
@@ -467,20 +476,6 @@ 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 +735,7 @@ static struct pcpu_chunk *pcpu_alloc_chunk(void)
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;
@@ -1129,6 +1124,7 @@ static void pcpu_balance_workfn(struct work_struct *work)
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 +1142,25 @@ static void pcpu_balance_workfn(struct work_struct *work)
pcpu_destroy_chunk(chunk);
}
+ /* service chunks which requested async area map extension */
+ 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 +1659,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
*/
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 +1688,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
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);

104
debian/patches/bugfix/all/percpu-fix-synchronization-between-synchronous-map-e.patch vendored Normal file
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@ -0,0 +1,104 @@
From: Tejun Heo <tj@kernel.org>
Date: Wed, 25 May 2016 11:48:25 -0400
Subject: percpu: fix synchronization between synchronous map extension and
chunk destruction
Origin: https://git.kernel.org/linus/6710e594f71ccaad8101bc64321152af7cd9ea28
For non-atomic allocations, pcpu_alloc() can try to extend the area
map synchronously after dropping pcpu_lock; however, the extension
wasn't synchronized against chunk destruction and the chunk might get
freed while extension is in progress.
This patch fixes the bug by putting most of non-atomic allocations
under pcpu_alloc_mutex to synchronize against pcpu_balance_work which
is responsible for async chunk management including destruction.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: stable@vger.kernel.org # v3.18+
Fixes: 1a4d76076cda ("percpu: implement asynchronous chunk population")
---
mm/percpu.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/mm/percpu.c b/mm/percpu.c
index b1d2a3844792..9903830aaebb 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -162,7 +162,7 @@ static struct pcpu_chunk *pcpu_reserved_chunk;
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 */
@@ -444,6 +444,8 @@ static int pcpu_extend_area_map(struct pcpu_chunk *chunk, int new_alloc)
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;
@@ -890,6 +892,9 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
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 */
@@ -962,12 +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;
}
@@ -978,7 +980,6 @@ restart:
spin_lock_irqsave(&pcpu_lock, flags);
}
- mutex_unlock(&pcpu_alloc_mutex);
goto restart;
area_found:
@@ -988,8 +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);
@@ -1000,7 +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;
@@ -1040,6 +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;
}

2
debian/patches/series vendored
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@ -113,6 +113,8 @@ bugfix/all/sched-panic-on-corrupted-stack-end.patch
bugfix/all/tipc-fix-an-infoleak-in-tipc_nl_compat_link_dump.patch
bugfix/all/rds-fix-an-infoleak-in-rds_inc_info_copy.patch
bugfix/all/keys-potential-uninitialized-variable.patch
bugfix/all/percpu-fix-synchronization-between-chunk-map_extend_.patch
bugfix/all/percpu-fix-synchronization-between-synchronous-map-e.patch
# ABI maintenance
debian/mips-siginfo-fix-abi-change-in-4.6.2.patch