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[160.39.33.242]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4a779e79c12sm3794321cf.53.2025.06.19.18.24.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Jun 2025 18:24:49 -0700 (PDT) From: Tal Zussman Date: Thu, 19 Jun 2025 21:24:23 -0400 Subject: [PATCH v3 1/4] userfaultfd: correctly prevent registering VM_DROPPABLE regions Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250619-uffd-fixes-v3-1-a7274d3bd5e4@columbia.edu> References: <20250619-uffd-fixes-v3-0-a7274d3bd5e4@columbia.edu> In-Reply-To: <20250619-uffd-fixes-v3-0-a7274d3bd5e4@columbia.edu> To: Andrew Morton , Peter Xu , "Jason A. Donenfeld" , David Hildenbrand , Alexander Viro , Christian Brauner , Jan Kara , Andrea Arcangeli Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Tal Zussman X-Mailer: b4 0.14.3-dev-d7477 X-Developer-Signature: v=1; a=ed25519-sha256; t=1750382688; l=1272; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=48H87QO2Pis/SoCKFWPY9K3keEwEH0YOZ4nBSSNwcvE=; b=anDw4BUOIaeEyJ5c4porbKpKkHrHAXlVWt+d9mp9dQbT/Aordkik+mDY6JLUsIbX3B3SmAthB I7FE0uQDxRzCy7TSGKnedagoQqrgduV4YtN885eaf3bwsgnhRjP1ODV X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Proofpoint-ORIG-GUID: JlGgFJ-rA-bf5eJh6Gekv33t53-NF-AJ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjIwMDAwOSBTYWx0ZWRfX4ax3rOh7rplh E7hW+o2r3Q+10k5wTveL2Pll6ak/Sfw96sEb4Paak7dW2ccGc6IwDJemltPZlH9cQYbWRxzUow9 zbU+Eq29RzCE6yV597nCf8og89U7io0Usmjyy1WyNktPrYTkvfvXL/iGR0a1p8q/kwVIOeU2O3W ZA0fBE8bK67aOUMrjDu5pKj5rkY45H4XLXEGpGzB2kLgSCwzRJ5Oa8VPpfq5F1XILjmmKRnag1L 5KzfJS0Nys1n9yiiCEq2p7oGycnim/TNFGNiQbfW+gR7vCWA70Pp0lQ4PkykbhYk0qQ2Gb82uoP 9Tc+GnlvG3NqDB5eQdODpfb/mqMtAtDXXwhJXshS3gAXwOMdEQ7cz+wleGNK2D5ui9W3GGNXhcl Gw/STN2/ X-Proofpoint-GUID: JlGgFJ-rA-bf5eJh6Gekv33t53-NF-AJ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-06-19_08,2025-06-18_03,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=927 clxscore=1015 bulkscore=10 phishscore=0 adultscore=0 mlxscore=0 spamscore=0 impostorscore=0 lowpriorityscore=10 malwarescore=0 priorityscore=1501 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2505160000 definitions=main-2506200009 vma_can_userfault() masks off non-userfaultfd VM flags from vm_flags. The vm_flags & VM_DROPPABLE test will then always be false, incorrectly allowing VM_DROPPABLE regions to be registered with userfaultfd. Additionally, vm_flags is not guaranteed to correspond to the actual VMA's flags. Fix this test by checking the VMA's flags directly. Link: https://lore.kernel.org/linux-mm/5a875a3a-2243-4eab-856f-bc53ccfec3ea= @redhat.com/ Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily f= reeable mappings") Acked-by: David Hildenbrand Acked-by: Peter Xu Acked-by: Jason A. Donenfeld Signed-off-by: Tal Zussman --- include/linux/userfaultfd_k.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 75342022d144..f3b3d2c9dd5e 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -218,7 +218,7 @@ static inline bool vma_can_userfault(struct vm_area_str= uct *vma, { vm_flags &=3D __VM_UFFD_FLAGS; =20 - if (vm_flags & VM_DROPPABLE) + if (vma->vm_flags & VM_DROPPABLE) return false; =20 if ((vm_flags & VM_UFFD_MINOR) && --=20 2.39.5