Messages in this thread Patch in this message | | | From | Mark Rutland <> | Subject | [PATCH] bpf: fix possible spectre-v1 in find_and_alloc_map() | Date | Thu, 3 May 2018 17:04:59 +0100 |
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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 --- kernel/bpf/syscall.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
I found this when running smatch over a v4.17-rc2 arm64 allyesconfig kernel.
IIUC this may allow for a speculative branch to an arbitrary gadget when we subsequently call ops->map_alloc_check(attr).
Mark.
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 4ca46df19c9a..8a7acd0dbeb6 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -26,6 +26,7 @@ #include <linux/cred.h> #include <linux/timekeeping.h> #include <linux/ctype.h> +#include <linux/nospec.h> #define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PROG_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) { const struct bpf_map_ops *ops; + u32 type = attr->map_type; struct bpf_map *map; int err; - if (attr->map_type >= ARRAY_SIZE(bpf_map_types)) + if (type >= ARRAY_SIZE(bpf_map_types)) 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) return ERR_PTR(-EINVAL); @@ -122,7 +125,7 @@ static struct bpf_map *find_and_alloc_map(union bpf_attr *attr) if (IS_ERR(map)) return map; map->ops = ops; - map->map_type = attr->map_type; + map->map_type = type; return map; } -- 2.11.0
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