bpf: fix allocation warnings in bpf maps and integer overflow
For large map->value_size the user space can trigger memory allocation warnings like:
WARNING: CPU: 2 PID: 11122 at mm/page_alloc.c:2989
__alloc_pages_nodemask+0x695/0x14e0()
Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff82743b56>] dump_stack+0x68/0x92 lib/dump_stack.c:50
[<ffffffff81244ec9>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:460
[<ffffffff812450f9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:493
[< inline >] __alloc_pages_slowpath mm/page_alloc.c:2989
[<ffffffff81554e95>] __alloc_pages_nodemask+0x695/0x14e0 mm/page_alloc.c:3235
[<ffffffff816188fe>] alloc_pages_current+0xee/0x340 mm/mempolicy.c:2055
[< inline >] alloc_pages include/linux/gfp.h:451
[<ffffffff81550706>] alloc_kmem_pages+0x16/0xf0 mm/page_alloc.c:3414
[<ffffffff815a1c89>] kmalloc_order+0x19/0x60 mm/slab_common.c:1007
[<ffffffff815a1cef>] kmalloc_order_trace+0x1f/0xa0 mm/slab_common.c:1018
[< inline >] kmalloc_large include/linux/slab.h:390
[<ffffffff81627784>] __kmalloc+0x234/0x250 mm/slub.c:3525
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] map_update_elem kernel/bpf/syscall.c:288
[< inline >] SYSC_bpf kernel/bpf/syscall.c:744
To avoid never succeeding kmalloc with order >= MAX_ORDER check that
elem->value_size and computed elem_size are within limits for both hash and
array type maps.
Also add __GFP_NOWARN to kmalloc(value_size | elem_size) to avoid OOM warnings.
Note kmalloc(key_size) is highly unlikely to trigger OOM, since key_size <= 512,
so keep those kmalloc-s as-is.
Large value_size can cause integer overflows in elem_size and map.pages
formulas, so check for that as well.
Fixes: aaac3ba95e4c ("bpf: charge user for creation of BPF maps and programs")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 19909b2..34777b37 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -64,12 +64,35 @@
*/
goto free_htab;
- err = -ENOMEM;
+ if (htab->map.value_size >= (1 << (KMALLOC_SHIFT_MAX - 1)) -
+ MAX_BPF_STACK - sizeof(struct htab_elem))
+ /* if value_size is bigger, the user space won't be able to
+ * access the elements via bpf syscall. This check also makes
+ * sure that the elem_size doesn't overflow and it's
+ * kmalloc-able later in htab_map_update_elem()
+ */
+ goto free_htab;
+
+ htab->elem_size = sizeof(struct htab_elem) +
+ round_up(htab->map.key_size, 8) +
+ htab->map.value_size;
+
/* prevent zero size kmalloc and check for u32 overflow */
if (htab->n_buckets == 0 ||
htab->n_buckets > U32_MAX / sizeof(struct hlist_head))
goto free_htab;
+ if ((u64) htab->n_buckets * sizeof(struct hlist_head) +
+ (u64) htab->elem_size * htab->map.max_entries >=
+ U32_MAX - PAGE_SIZE)
+ /* make sure page count doesn't overflow */
+ goto free_htab;
+
+ htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
+ htab->elem_size * htab->map.max_entries,
+ PAGE_SIZE) >> PAGE_SHIFT;
+
+ err = -ENOMEM;
htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct hlist_head),
GFP_USER | __GFP_NOWARN);
@@ -85,13 +108,6 @@
raw_spin_lock_init(&htab->lock);
htab->count = 0;
- htab->elem_size = sizeof(struct htab_elem) +
- round_up(htab->map.key_size, 8) +
- htab->map.value_size;
-
- htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
- htab->elem_size * htab->map.max_entries,
- PAGE_SIZE) >> PAGE_SHIFT;
return &htab->map;
free_htab:
@@ -222,7 +238,7 @@
WARN_ON_ONCE(!rcu_read_lock_held());
/* allocate new element outside of lock */
- l_new = kmalloc(htab->elem_size, GFP_ATOMIC);
+ l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
if (!l_new)
return -ENOMEM;