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[70.52.229.124]) by smtp.gmail.com with ESMTPSA id u13-20020a0cc48d000000b005ead602acfesm2669536qvi.35.2023.04.12.09.39.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Apr 2023 09:39:24 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Leonardo Bras Soares Passos , Andrea Arcangeli , Axel Rasmussen , Nadav Amit , Andrew Morton , Mike Rapoport , Mike Kravetz , David Hildenbrand , peterx@redhat.com, Dmitry Safonov <0x7f454c46@gmail.com>, linux-stable Subject: [PATCH v2 01/31] Revert "userfaultfd: don't fail on unrecognized features" Date: Wed, 12 Apr 2023 12:38:52 -0400 Message-Id: <20230412163922.327282-2-peterx@redhat.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230412163922.327282-1-peterx@redhat.com> References: <20230412163922.327282-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This is a proposal to revert commit 914eedcb9ba0ff53c33808. I found this when writting a simple UFFDIO_API test to be the first unit test in this set. Two things breaks with the commit: - UFFDIO_API check was lost and missing. According to man page, the kernel should reject ioctl(UFFDIO_API) if uffdio_api.api !=3D 0xaa. This check is needed if the api version will be extended in the future, or user app won't be able to identify which is a new kernel. - Feature flags checks were removed, which means UFFDIO_API with a feature that does not exist will also succeed. According to the man page, we should (and it makes sense) to reject ioctl(UFFDIO_API) if unknown features passed in. Link: https://lore.kernel.org/r/20220722201513.1624158-1-axelrasmussen@goog= le.com Fixes: 914eedcb9ba0 ("userfaultfd: don't fail on unrecognized features") Cc: Axel Rasmussen Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Mike Rapoport Cc: linux-stable Acked-by: David Hildenbrand Signed-off-by: Peter Xu --- fs/userfaultfd.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 8395605790f6..3b2a41c330e6 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1977,8 +1977,10 @@ static int userfaultfd_api(struct userfaultfd_ctx *c= tx, ret =3D -EFAULT; if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) goto out; - /* Ignore unsupported features (userspace built against newer kernel) */ - features =3D uffdio_api.features & UFFD_API_FEATURES; + features =3D uffdio_api.features; + ret =3D -EINVAL; + if (uffdio_api.api !=3D UFFD_API || (features & ~UFFD_API_FEATURES)) + goto err_out; ret =3D -EPERM; if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE)) goto err_out; --=20 2.39.1