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Fri, 21 Mar 2025 15:16:48 -0700 (PDT) Message-ID: <44d4adae6a5398dcd97afbe2c922f8c9a71598f2.camel@gmail.com> Subject: Re: [PATCH v2 bpf-next 1/2] bpf: Fix out-of-bounds read in check_atomic_load/store() From: Eduard Zingerman To: Kohei Enju , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Peilin Ye , Ilya Leoshkevich , Kuniyuki Iwashima , kohei.enju@gmail.com, syzbot+a5964227adc0f904549c@syzkaller.appspotmail.com Date: Fri, 21 Mar 2025 15:16:43 -0700 In-Reply-To: <20250321110010.95217-5-enjuk@amazon.com> References: <20250321110010.95217-4-enjuk@amazon.com> <20250321110010.95217-5-enjuk@amazon.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-03-21 at 19:59 +0900, Kohei Enju wrote: > syzbot reported the following splat [0]. >=20 > In check_atomic_load/store(), register validity is not checked before > atomic_ptr_type_ok(). This causes the out-of-bounds read in is_ctx_reg() > called from atomic_ptr_type_ok() when the register number is MAX_BPF_REG > or greater. >=20 > Let's call check_load_mem()/check_store_reg() before atomic_ptr_type_ok() > to avoid the OOB read. [...] > Memory state around the buggy address: > ffff888141b0d580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff888141b0d600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > >ffff888141b0d680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ^ > ffff888141b0d700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff888141b0d780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >=20 > Reported-by: syzbot+a5964227adc0f904549c@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3Da5964227adc0f904549c > Tested-by: syzbot+a5964227adc0f904549c@syzkaller.appspotmail.com > Fixes: e24bbad29a8d ("bpf: Introduce load-acquire and store-release instr= uctions") > Fixes: ff3afe5da998 ("selftests/bpf: Add selftests for load-acquire and s= tore-release instructions") > Signed-off-by: Kohei Enju > --- Acked-by: Eduard Zingerman [...]