bpf: Fix hashtab overflow check on 32-bit arches

stable inclusion
from stable-v4.19.311
commit 33ec04cadb77605b71d9298311919303d390c4d5
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9HK6X
CVE: CVE-2024-26884

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=33ec04cadb77



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[ Upstream commit 6787d916c2cf9850c97a0a3f73e08c43e7d973b1 ]

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: daaf427c ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Pu Lehui <pulehui@huawei.com>