mirror of
https://github.com/torvalds/linux
synced 2024-09-06 18:01:05 +00:00
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: daaf427c6a
("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>
This commit is contained in:
parent
281d464a34
commit
6787d916c2
|
@ -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);
|
||||
|
|
Loading…
Reference in a new issue