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bpf: fix possible spectre-v1 in find_and_alloc_map()

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It's possible for userspace to control attr->map_type. Sanitize it when
using it as an array index to prevent an out-of-bounds value being used
under speculation.

Found by smatch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: netdev@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Mark Rutland 2018-05-03 17:04:59 +01:00 committed by Daniel Borkmann
parent a8d7aa17bb
commit 9ef09e35e5
1 changed files with 6 additions and 3 deletions
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9
kernel/bpf/syscall.c
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@ -26,6 +26,7 @@
#include <linux/cred.h> #include <linux/cred.h>
#include <linux/timekeeping.h> #include <linux/timekeeping.h>
#include <linux/ctype.h> #include <linux/ctype.h>
#include <linux/nospec.h>
#define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PROG_ARRAY || \ #define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PROG_ARRAY || \
(map)->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY || \ (map)->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY || \
@ -102,12 +103,14 @@ const struct bpf_map_ops bpf_map_offload_ops = {
static struct bpf_map *find_and_alloc_map(union bpf_attr *attr) static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
{ {
const struct bpf_map_ops *ops; const struct bpf_map_ops *ops;
u32 type = attr->map_type;
struct bpf_map *map; struct bpf_map *map;
int err; int err;
if (attr->map_type >= ARRAY_SIZE(bpf_map_types)) if (type >= ARRAY_SIZE(bpf_map_types))
return ERR_PTR(-EINVAL); return ERR_PTR(-EINVAL);
ops = bpf_map_types[attr->map_type]; type = array_index_nospec(type, ARRAY_SIZE(bpf_map_types));
ops = bpf_map_types[type];
if (!ops) if (!ops)
return ERR_PTR(-EINVAL); return ERR_PTR(-EINVAL);
@ -122,7 +125,7 @@ static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
if (IS_ERR(map)) if (IS_ERR(map))
return map; return map;
map->ops = ops; map->ops = ops;
map->map_type = attr->map_type; map->map_type = type;
return map; return map;
} }