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Thu, 18 Apr 2024 00:59:30 -0700 (PDT) MIME-Version: 1.0 References: <000000000000fe696d0615f120bb@google.com> <20240415131837.411c6e05eb7b0af077d6424a@linux-foundation.org> In-Reply-To: From: Alexander Potapenko Date: Thu, 18 Apr 2024 09:58:48 +0200 Message-ID: Subject: Re: [syzbot] [mm?] KMSAN: kernel-infoleak in bpf_probe_write_user To: Alexei Starovoitov Cc: Andrew Morton , syzbot , LKML , linux-mm , syzkaller-bugs , bpf Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 5084E14001C X-Stat-Signature: 9i1y78xqxo7eqi7dfxthowyhp3nyig74 X-HE-Tag: 1713427171-598842 X-HE-Meta: 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 aT6somH0 2vXK9H6LAc9SbWJMbSdmltx0DA2Krgh5PDQlDlWKvHbcxtTMMSBBO2TD+UOs6j1suTF6DcziipOoGYCg561lvAD2gwO0rwBd6ZKNu+iA80UdjcVvhGrfxuJcBk7MS4gJgCU6WfbXvRqsFklG/kQC/CjxohyczuFQ5+Tgpj+4h669TNt971i8sUaf784VKGmac1MjkeYq03gPFnzSnEKdSCRWlZ4jvlk7vl48SJ8foWzCw8+HtMfFhCfMQrb3gv18fi8eItO3nAy2eikp9VfmmOv7mvuE7p1aN2JhlJjL5S2UxRMT05mY5hxm+F9cvIGMfi6A8obDaK6+usDX44uHs6tM4G4lytFzpK0rFWwVo1WcHS8AugSG46OUnrAsILhY/zTwkTC8LBQb2X1KtIWUGN0iJMkQJdJqNLFJBQMdOE0peoXeeK9lLGZcD4S1c9cVKkoyu+aLmBLhalGY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 5:16=E2=80=AFPM Alexei Starovoitov wrote: > > 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= . Out of curiosity, is this feature supposed to be used in production kernels= ? > And recently we added > commit e8742081db7d ("bpf: Mark bpf prog stack with > kmsan_unposion_memory in interpreter mode") > to shut up syzbot. I checked that the report in question is not reproducible with this patch anymore. Let's just wait until it reaches the mainline.