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Wed, 17 Jun 2026 09:28:09 -0700 (PDT) Received: from john-p8 ([98.97.43.63]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c42fbb5b79sm167243115ad.36.2026.06.17.09.28.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Jun 2026 09:28:08 -0700 (PDT) Date: Wed, 17 Jun 2026 09:28:07 -0700 From: John Fastabend To: Jiayuan Chen Cc: bpf@vger.kernel.org Subject: Re: [PATCH bpf-next v4 1/6] bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() Message-ID: References: <20260615021959.140010-1-jiayuan.chen@linux.dev> <20260615021959.140010-2-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20260615021959.140010-2-jiayuan.chen@linux.dev> On Mon, Jun 15, 2026 at 10:19:54AM +0800, Jiayuan Chen wrote: >From: Weiming Shi > >When the scatterlist ring is full or nearly full, bpf_msg_push_data() >enters a copy fallback path and computes copy + len for the page >allocation size. Since len comes from BPF with arg3_type = ARG_ANYTHING >and both are u32, a crafted len can wrap the sum to a small value, >causing an undersized allocation followed by an out-of-bounds memcpy. > > BUG: unable to handle page fault for address: ffffed104089a402 > Oops: Oops: 0000 [#1] SMP KASAN NOPTI > Call Trace: > __asan_memcpy (mm/kasan/shadow.c:105) > bpf_msg_push_data (net/core/filter.c:2852 net/core/filter.c:2788) > bpf_prog_9ed8b5711920a7d7+0x2e/0x36 > sk_psock_msg_verdict (net/core/skmsg.c:934) > tcp_bpf_sendmsg (net/ipv4/tcp_bpf.c:421 net/ipv4/tcp_bpf.c:584) > __sys_sendto (net/socket.c:2206) > do_syscall_64 (arch/x86/entry/syscall_64.c:94) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) > >Add an overflow check before the allocation. > >Link: https://lore.kernel.org/all/20260424155913.A19FDC19425@smtp.kernel.org >Fixes: 6fff607e2f14 ("bpf: sk_msg program helper bpf_msg_push_data") >Tested-by: Xiang Mei >Tested-by: Xinyu Ma >Reviewed-by: Jiayuan Chen >Reviewed-by: Emil Tsalapatis >Reviewed-by: Kuniyuki Iwashima >Signed-off-by: Weiming Shi >Signed-off-by: Jiayuan Chen Reviewed-by: John Fastabend