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Jones" , akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org Cc: Eric Dumazet , Josef Bacik , Jens Axboe , linux-kernel , netdev@vger.kernel.org, Eric Dumazet , syzbot+e1cd6bd8493060bd701d@syzkaller.appspotmail.com, Mike Christie , Yu Kuai , linux-block@vger.kernel.org, nbd@other.debian.org Subject: Userland used in writeback path was Re: [PATCH] nbd: restrict sockets to TCP and UDP Message-ID: References: <20250909132243.1327024-1-edumazet@google.com> <20251118181623.GK1427@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="aQHk9D/h+j/L8Oa2" Content-Disposition: inline In-Reply-To: <20251118181623.GK1427@redhat.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 391FD14000A X-Stat-Signature: cooqcm371ufnpu91copmfqbio8m6phz3 X-Rspam-User: X-HE-Tag: 1763543440-499682 X-HE-Meta: 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 hZgSol/z cz4qDHc7b9VgxyC5KcPZxqWt1mJ6A3/00vsVSz+Po2KqBwKYVL84tG77/OyQQ1BdQ7gaLiXS108iT/efGF0FSoHjCZvLXmU3OOe6biAKKr+9M47ZZ8pVytQo1vI6ifEjNzTZ2r5SI/W0KkM12dEbkNWi6Z2J1RwT8CPYXSCLdS+acUibaV93YzDzcIJJ536eG4AQZPHOIqfMWRz0urJRYIxvG2N0Ick5znNXJLzblh1FCyEeOw+ywyTWJy8eKBm8Sm/qoOIVFyDy4Ay6v+rZf3yO3MUhChREUUPrA07XA/98Pmz8BWSUqWKqX3VE+Qg2JGjMOuC8Ros9PR9GI74KnyzXLdFaSROtTyUwVHQ90tOke1uazXVXzTvLMHCWJWjJ8mIUsEUIIg/PV+4A= 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: --aQHk9D/h+j/L8Oa2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue 2025-11-18 18:16:23, Richard W.M. Jones wrote: > On Tue, Nov 18, 2025 at 06:56:33PM +0100, Pavel Machek wrote: > > Hi! > >=20 > > > Recently, syzbot started to abuse NBD with all kinds of sockets. > > >=20 > > > Commit cf1b2326b734 ("nbd: verify socket is supported during setup") > > > made sure the socket supported a shutdown() method. > > >=20 > > > Explicitely accept TCP and UNIX stream sockets. > >=20 > > Note that running nbd server and client on same machine is not safe in > > read-write mode. It may deadlock under low memory conditions. > >=20 > > Thus I'm not sure if we should accept UNIX sockets. >=20 > Both nbd-client and nbdkit have modes where they can mlock themselves > into RAM. kernel needs memory. It issues write-back to get some. nbd-client does syscall. Maybe writing to storage? That syscall does kmalloc(). That kmalloc now needs something like PF_MEMALLOC flag. mlock() is not enough. Best regards, Pavel --=20 I don't work for Nazis and criminals, and neither should you. Boycott Putin, Trump, Netanyahu and Musk! --aQHk9D/h+j/L8Oa2 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABECAB0WIQRPfPO7r0eAhk010v0w5/Bqldv68gUCaR2JjQAKCRAw5/Bqldv6 8nyLAJ0fg+14AbZ5oZZJCws638BzTfOy3ACfQZ9jf5rMfhYV1RriNRoroGv0JwI= =eRuh -----END PGP SIGNATURE----- --aQHk9D/h+j/L8Oa2--