From 01b3f52157ff5a47d6d8d796f396a4b34a53c61d Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Sun, 29 Nov 2015 16:59:35 -0800 Subject: [PATCH] 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 [] dump_stack+0x68/0x92 lib/dump_stack.c:50 [] warn_slowpath_common+0xd9/0x140 kernel/panic.c:460 [] warn_slowpath_null+0x29/0x30 kernel/panic.c:493 [< inline >] __alloc_pages_slowpath mm/page_alloc.c:2989 [] __alloc_pages_nodemask+0x695/0x14e0 mm/page_alloc.c:3235 [] alloc_pages_current+0xee/0x340 mm/mempolicy.c:2055 [< inline >] alloc_pages include/linux/gfp.h:451 [] alloc_kmem_pages+0x16/0xf0 mm/page_alloc.c:3414 [] kmalloc_order+0x19/0x60 mm/slab_common.c:1007 [] kmalloc_order_trace+0x1f/0xa0 mm/slab_common.c:1018 [< inline >] kmalloc_large include/linux/slab.h:390 [] __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 Signed-off-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/arraymap.c | 8 +++++++- kernel/bpf/hashtab.c | 34 +++++++++++++++++++++++++--------- kernel/bpf/syscall.c | 4 ++-- 3 files changed, 34 insertions(+), 12 deletions(-) diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index 4c67ce39732e..b0799bced518 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -28,11 +28,17 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) attr->value_size == 0) return ERR_PTR(-EINVAL); + if (attr->value_size >= 1 << (KMALLOC_SHIFT_MAX - 1)) + /* if value_size is bigger, the user space won't be able to + * access the elements. + */ + return ERR_PTR(-E2BIG); + elem_size = round_up(attr->value_size, 8); /* check round_up into zero and u32 overflow */ if (elem_size == 0 || - attr->max_entries > (U32_MAX - sizeof(*array)) / elem_size) + attr->max_entries > (U32_MAX - PAGE_SIZE - sizeof(*array)) / elem_size) return ERR_PTR(-ENOMEM); array_size = sizeof(*array) + attr->max_entries * elem_size; diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 19909b22b4f8..34777b3746fa 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -64,12 +64,35 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) */ 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 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) 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 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value, 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; diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 4a8f3c1d7da6..3b39550d8485 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -240,7 +240,7 @@ static int map_lookup_elem(union bpf_attr *attr) goto free_key; err = -ENOMEM; - value = kmalloc(map->value_size, GFP_USER); + value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN); if (!value) goto free_key; @@ -299,7 +299,7 @@ static int map_update_elem(union bpf_attr *attr) goto free_key; err = -ENOMEM; - value = kmalloc(map->value_size, GFP_USER); + value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN); if (!value) goto free_key;