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[146.241.68.231]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39c0b79e33asm13588688f8f.66.2025.04.01.01.00.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Apr 2025 01:00:57 -0700 (PDT) Message-ID: <89dcde93-8e5a-4193-aa01-fde5dd5ee1fd@redhat.com> Date: Tue, 1 Apr 2025 10:00:56 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] net: decrease cached dst counters in dst_release To: Antoine Tenart , davem@davemloft.net, kuba@kernel.org, edumazet@google.com Cc: netdev@vger.kernel.org References: <20250326173634.31096-1-atenart@kernel.org> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20250326173634.31096-1-atenart@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/26/25 6:36 PM, Antoine Tenart wrote: > Upstream fix ac888d58869b ("net: do not delay dst_entries_add() in > dst_release()") moved decrementing the dst count from dst_destroy to > dst_release to avoid accessing already freed data in case of netns > dismantle. However in case CONFIG_DST_CACHE is enabled and OvS+tunnels > are used, this fix is incomplete as the same issue will be seen for > cached dsts: > > Unable to handle kernel paging request at virtual address ffff5aabf6b5c000 > Call trace: > percpu_counter_add_batch+0x3c/0x160 (P) > dst_release+0xec/0x108 > dst_cache_destroy+0x68/0xd8 > dst_destroy+0x13c/0x168 > dst_destroy_rcu+0x1c/0xb0 > rcu_do_batch+0x18c/0x7d0 > rcu_core+0x174/0x378 > rcu_core_si+0x18/0x30 > > Fix this by invalidating the cache, and thus decrementing cached dst > counters, in dst_release too. > > Fixes: d71785ffc7e7 ("net: add dst_cache to ovs vxlan lwtunnel") > Signed-off-by: Antoine Tenart > --- > net/core/dst.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/net/core/dst.c b/net/core/dst.c > index 9552a90d4772..6d76b799ce64 100644 > --- a/net/core/dst.c > +++ b/net/core/dst.c > @@ -165,6 +165,14 @@ static void dst_count_dec(struct dst_entry *dst) > void dst_release(struct dst_entry *dst) > { > if (dst && rcuref_put(&dst->__rcuref)) { > +#ifdef CONFIG_DST_CACHE > + if (dst->flags & DST_METADATA) { > + struct metadata_dst *md_dst = (struct metadata_dst *)dst; > + > + if (md_dst->type == METADATA_IP_TUNNEL) > + dst_cache_reset_now(&md_dst->u.tun_info.dst_cache); I think the fix is correct, but I'm wondering if we have a similar issue for the METADATA_XFRM meta-dst. Isn't: dst_release(md_dst->u.xfrm_info.dst_orig); in metadata_dst_free() going to cause the same UaF? Why don't we need to clean such dst here, too? Thanks! Paolo