KASAN reports following splat: BUG: KASAN: slab-out-of-bounds in pipapo_get_avx2+0x941/0x25d0 Read of size 1 at addr ffff88814c561be0 by task nft/3944 Call Trace: pipapo_get_avx2+0x941/0x25d0 nft_pipapo_insert+0x440/0x11b0 nf_tables_newsetelem+0x220a/0x3a00 .. This bisects to commit 84c1da7b38d9 ("netfilter: nft_set_pipapo: use AVX2 algorithm for insertions too"). However, that change merely uncovers this bug. When we find a match but that match has expired or timed out, the AVX2 implementation restarts the full match loop. At that point, the pointer to the key data has already been changed and points to the keys last field. This will then result in out-of-bounds read once its incremented again for the next field. The restart logic in AVX2 is different compared to the plain C implementation, but both should follow the same logic. The C implementation just calls pipapo_refill() again do check the next entry. Do the same in the AVX2 implementation. Note that with this change, due to implementation differences of pipapo_refill vs. nft_pipapo_avx2_refill, the refill call will return the same element again. Then, on the next call, it will move to the next entry as expected. This is because avx2_refill doesn't clear the bitmap in the 'last' conditional. This is harmless. Expired/timed out elements are also not expected to be frequent. selftest is added in a followup commit. Fixes: 7400b063969b ("nft_set_pipapo: Introduce AVX2-based lookup implementation") Reviewed-by: Stefano Brivio Signed-off-by: Florian Westphal --- net/netfilter/nft_set_pipapo_avx2.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/netfilter/nft_set_pipapo_avx2.c b/net/netfilter/nft_set_pipapo_avx2.c index e72fd045d037..7ff90325c97f 100644 --- a/net/netfilter/nft_set_pipapo_avx2.c +++ b/net/netfilter/nft_set_pipapo_avx2.c @@ -1179,7 +1179,6 @@ struct nft_pipapo_elem *pipapo_get_avx2(const struct nft_pipapo_match *m, nft_pipapo_avx2_prepare(); -next_match: nft_pipapo_for_each_field(f, i, m) { bool last = i == m->field_count - 1, first = !i; int ret = 0; @@ -1226,6 +1225,7 @@ struct nft_pipapo_elem *pipapo_get_avx2(const struct nft_pipapo_match *m, #undef NFT_SET_PIPAPO_AVX2_LOOKUP +next_match: if (ret < 0) { scratch->map_index = map_index; kernel_fpu_end(); @@ -1238,8 +1238,11 @@ struct nft_pipapo_elem *pipapo_get_avx2(const struct nft_pipapo_match *m, e = f->mt[ret].e; if (unlikely(__nft_set_elem_expired(&e->ext, tstamp) || - !nft_set_elem_active(&e->ext, genmask))) + !nft_set_elem_active(&e->ext, genmask))) { + ret = pipapo_refill(res, f->bsize, f->rules, + fill, f->mt, last); goto next_match; + } scratch->map_index = map_index; kernel_fpu_end(); -- 2.49.1