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authorJiri Slaby <jslaby@suse.cz>2018-01-12 17:34:16 +0100
committerJiri Slaby <jslaby@suse.cz>2018-01-12 17:47:44 +0100
commit859886c98e0735820a5a15c3d725657f69ad74fa (patch)
treea434dfc4b3981d37095f301b16bfdbfa86c933db
parent4a5f2905d288c38afb6afbb69f12285922884ac9 (diff)
bpf, array: fix overflow in max_entries and undefined behavior
in index_mask (bsc#1068032 CVE-2017-5753). suse-commit: 110eda037a161143f04480d9af979bc27f320c97
-rw-r--r--kernel/bpf/arraymap.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 56f8a8306a49..3608fa1aec8a 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -23,6 +23,7 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
u32 elem_size, array_size, index_mask, max_entries;
bool unpriv = !capable(CAP_SYS_ADMIN);
struct bpf_array *array;
+ u64 mask64;
/* check sanity of attributes */
if (attr->max_entries == 0 || attr->key_size != 4 ||
@@ -38,13 +39,25 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
elem_size = round_up(attr->value_size, 8);
max_entries = attr->max_entries;
- index_mask = roundup_pow_of_two(max_entries) - 1;
- if (unpriv)
+ /* On 32 bit archs roundup_pow_of_two() with max_entries that has
+ * upper most bit set in u32 space is undefined behavior due to
+ * resulting 1U << 32, so do it manually here in u64 space.
+ */
+ mask64 = fls_long(max_entries - 1);
+ mask64 = 1ULL << mask64;
+ mask64 -= 1;
+
+ index_mask = mask64;
+ if (unpriv) {
/* round up array size to nearest power of 2,
* since cpu will speculate within index_mask limits
*/
max_entries = index_mask + 1;
+ /* Check for overflows. */
+ if (max_entries < attr->max_entries)
+ return ERR_PTR(-E2BIG);
+ }
/* check round_up into zero and u32 overflow */
if (elem_size == 0 ||