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AJvYcCUCm6AQHWqlgNEwMk4M9OsdqVhxYq8PGwJAgmuCYXVAN8ooIZTxqMr7064Q08acRaxs8LNneOO09MbtUkokTUqC2z8= X-Gm-Message-State: AOJu0YxYMtX6bqQwsZdsPWk0JWJbxv45Ui+/nwsbgfCB14K86I3x7gay PI7oClzKtAEkbzxONAPwU8lhM8PJm1QQpuizWGN1YWMuaZKq+4vFMhTnyhp5nNyxIW3QaunNeRy GB554QK2gdHpb2L15UFR38N044+s= X-Google-Smtp-Source: AGHT+IF8Nl0MMpxdCBz7YOuqSPmL6zOTDD6DeortoGI1yNBvpT1TYwnUZsl3dePdOGnb7RaFfhoArAxG453LTbO1ZSg= X-Received: by 2002:a05:6000:4c5:b0:346:ba70:f262 with SMTP id h5-20020a05600004c500b00346ba70f262mr9409969wri.14.1713280572902; Tue, 16 Apr 2024 08:16:12 -0700 (PDT) MIME-Version: 1.0 References: <000000000000fe696d0615f120bb@google.com> <20240415131837.411c6e05eb7b0af077d6424a@linux-foundation.org> In-Reply-To: From: Alexei Starovoitov Date: Tue, 16 Apr 2024 08:16:01 -0700 Message-ID: Subject: Re: [syzbot] [mm?] KMSAN: kernel-infoleak in bpf_probe_write_user To: Alexander Potapenko Cc: Andrew Morton , syzbot , LKML , linux-mm , syzkaller-bugs , bpf Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: AD68B100016 X-Rspam-User: X-Stat-Signature: afq5q4ubb4536twaqem44hio1tih9stg X-HE-Tag: 1713280574-144381 X-HE-Meta: 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 iVq+KNyE 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000577, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 16, 2024 at 1:52=E2=80=AFAM Alexander Potapenko wrote: > > On Mon, Apr 15, 2024 at 11:06=E2=80=AFPM Alexei Starovoitov > wrote: > > > > Hi, > > > > syzbot folks, please disable such "bug" reporting. > > The whole point of bpf is to pass such info to userspace. > > probe_write_user, various ring buffers, bpf_*_printk-s, bpf maps > > all serve this purpose of "infoleak". > > > > Hi Alexei, > > From KMSAN's perspective it is fine to pass information to the > userspace, unless it is marked as uninitialized. > It could be that we are missing some initialization in kernel/bpf/core.c = though. > Do you know which part of the code is supposed to initialize the stack > in PROG_NAME? cap_bpf + cap_perfmon bpf program are allowed to read uninitialized stack. And recently we added commit e8742081db7d ("bpf: Mark bpf prog stack with kmsan_unposion_memory in interpreter mode") to shut up syzbot.