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[95.117.40.97]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a178db8c6dsm62744995e9.14.2026.10.05.21.39.36 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 05 Oct 2026 21:39:37 -0700 (PDT) From: Karl Mehltretter To: Namjae Jeon Cc: Karl Mehltretter , Hyunchul Lee , ntfs@lists.linux.dev, stable@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 0/2] ntfs: fix two kmap_local bugs on 32-bit kernels Date: Tue, 6 Oct 2026 06:38:07 +0200 Message-Id: <20261006043810.5393-1-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Two kmap_local bugs in the mount path of fs/ntfs. Both only show on 32-bit kernels with HIGHMEM, where kmap_local_folio() hands out fixmap slots from a per task stack of 16 entries. multi_v7_defconfig enables both NTFS_FS and HIGHMEM, so the stock 32-bit ARM configuration is affected. Patch 1: check_mft_mirror() unmaps pointers that were advanced past the end of the page. On 32-bit ARM this clears the wrong fixmap entry and the mount dies with a BUG a few calls later. syzkaller found it on a multi_v7_defconfig kernel. A fresh mkntfs volume reproduces it on the first mount. Patch 2: ntfs_check_logfile() maps the same page once per loop iteration and unmaps it once, so a mount leaves three entries on the stack of the mounting task. After one mount the CPU it ran on can no longer be taken offline. A process that mounts ntfs volumes five times hits the BUG_ON() in kmap_local_idx_push(). x86-32 also warns when mount(2) returns. The two fixes are independent of each other. Patch 2 was tested on top of patch 1. Both were tested on 32-bit ARM and x86-32 in QEMU. Details are below the --- line of each patch. Karl Mehltretter (2): ntfs: fix kunmap_local() of advanced pointers in check_mft_mirror() ntfs: fix kmap_local leak in ntfs_check_logfile() fs/ntfs/logfile.c | 11 ++++++----- fs/ntfs/super.c | 20 +++++++++++--------- 2 files changed, 17 insertions(+), 14 deletions(-) base-commit: 551c722f40809618230001baccf219193e22fc5a -- 2.53.0