diff options
| author | Toke Høiland-Jørgensen | 2024-03-07 13:03:36 +0100 |
|---|---|---|
| committer | Alexei Starovoitov | 2024-03-07 20:05:56 -0800 |
| commit | 6787d916c2cf9850c97a0a3f73e08c43e7d973b1 (patch) | |
| tree | 4507c251124f0b366db3aeaa34baa51fac562d67 /kernel/bpf | |
| parent | 281d464a34f540de166cee74b723e97ac2515ec3 (diff) | |
bpf: Fix hashtab overflow check on 32-bit arches
The hashtab code relies on roundup_pow_of_two() to compute the number of
hash buckets, and contains an overflow check by checking if the
resulting value is 0. However, on 32-bit arches, the roundup code itself
can overflow by doing a 32-bit left-shift of an unsigned long value,
which is undefined behaviour, so it is not guaranteed to truncate
neatly. This was triggered by syzbot on the DEVMAP_HASH type, which
contains the same check, copied from the hashtab code. So apply the same
fix to hashtab, by moving the overflow check to before the roundup.
Fixes: daaf427c6ab3 ("bpf: fix arraymap NULL deref and missing overflow and zero size checks")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Message-ID: <20240307120340.99577-3-toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/hashtab.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 03a6a2500b6a..3a088a5349bc 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -499,7 +499,13 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) num_possible_cpus()); } - /* hash table size must be power of 2 */ + /* hash table size must be power of 2; roundup_pow_of_two() can overflow + * into UB on 32-bit arches, so check that first + */ + err = -E2BIG; + if (htab->map.max_entries > 1UL << 31) + goto free_htab; + htab->n_buckets = roundup_pow_of_two(htab->map.max_entries); htab->elem_size = sizeof(struct htab_elem) + @@ -509,10 +515,8 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) else htab->elem_size += round_up(htab->map.value_size, 8); - err = -E2BIG; - /* prevent zero size kmalloc and check for u32 overflow */ - if (htab->n_buckets == 0 || - htab->n_buckets > U32_MAX / sizeof(struct bucket)) + /* check for u32 overflow */ + if (htab->n_buckets > U32_MAX / sizeof(struct bucket)) goto free_htab; err = bpf_map_init_elem_count(&htab->map); |