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authorJiri Slaby <jslaby@suse.cz>2018-01-12 17:34:16 +0100
committerJiri Slaby <jslaby@suse.cz>2018-01-12 17:35:09 +0100
commit30459072a60bc8b8f281b9170fc894f7cc3abc01 (patch)
tree5306c6841d47de9ce265c274def8e4bb3312dd2d
parent9270e0e8090984ef1556414d038ef00fce175e4f (diff)
bpf, array: fix overflow in max_entries and undefined behavior
in index_mask (bsc#1068032 CVE-2017-5753). suse-commit: 3283516d37a349ceeb90630650c41e99f9c7593c
-rw-r--r--kernel/bpf/arraymap.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 42a1227bf7ef..a4ae1ca44a57 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -53,7 +53,7 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
u32 elem_size, index_mask, max_entries;
bool unpriv = !capable(CAP_SYS_ADMIN);
struct bpf_array *array;
- u64 array_size;
+ u64 array_size, mask64;
/* check sanity of attributes */
if (attr->max_entries == 0 || attr->key_size != 4 ||
@@ -70,13 +70,25 @@ 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);
+ }
array_size = sizeof(*array);
if (percpu)