Commit 66f98c80 authored May 07, 2024 by Toke Høiland-Jørgensen Committed by g30012805 May 07, 2024

bpf: Fix DEVMAP_HASH overflow check on 32-bit arches

stable inclusion
from stable-v5.10.214
commit 225da02acdc97af01b6bc6ce1a3e5362bf01d3fb
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9HK1R
CVE: CVE-2024-26885

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=225da02acdc9

--------------------------------

[ Upstream commit 281d464a34f540de166cee74b723e97ac2515ec3 ]

The devmap code allocates a number hash buckets equal to the next power
of two of the max_entries value provided when creating the map. When
rounding up to the next power of two, the 32-bit variable storing the
number of buckets can overflow, and the code checks for overflow by
checking if the truncated 32-bit value is equal to 0. However, on 32-bit
arches the rounding up itself can overflow mid-way through, because it
ends up doing a left-shift of 32 bits on an unsigned long value. If the
size of an unsigned long is four bytes, this is undefined behaviour, so
there is no guarantee that we'll end up with a nice and tidy 0-value at
the end.

Syzbot managed to turn this into a crash on arm32 by creating a
DEVMAP_HASH with max_entries > 0x80000000 and then trying to update it.
Fix this by moving the overflow check to before the rounding up
operation.

Fixes: 6f9d451a ("xdp: Add devmap_hash map type for looking up devices by hashed index")
Link: https://lore.kernel.org/r/000000000000ed666a0611af6818@google.com


Reported-and-tested-by:  <syzbot+8cd36f6b65f3cafd400a@syzkaller.appspotmail.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Message-ID: <20240307120340.99577-2-toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Conflicts:
	kernel/bpf/devmap.c
Signed-off-by: Pu Lehui <pulehui@huawei.com>

parent 93f42c5d

kernel/bpf/devmap.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -131,10 +131,13 @@ static int dev_map_init_map(struct bpf_dtab dtab, union bpf_attr attr)
		bpf_map_init_from_attr(&dtab->map, attr);

		if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
		dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);

		if (!dtab->n_buckets) /* Overflow check */
		/* hash table size must be power of 2; roundup_pow_of_two() can
		* overflow into UB on 32-bit arches, so check that first
		*/
		if (dtab->map.max_entries > 1UL << 31)
		return -EINVAL;

		dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);
		cost += (u64) sizeof(struct hlist_head) * dtab->n_buckets;
		} else {
		cost += (u64) dtab->map.max_entries * sizeof(struct bpf_dtab_netdev *);