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Tue, 18 Aug 2026 02:45:34 -0700 (PDT) From: Hyunchul Lee To: Namjae Jeon Cc: Hyunchul Lee , ntfs@lists.linux.dev, rtm@csail.mit.edu, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] ntfs: reject invalid MFT LCNs from boot sector Date: Tue, 18 Aug 2026 18:45:20 +0900 Message-ID: <20260818-fix-negative-mft-lcn-v1-1-b7b0b206f2da@gmail.com> X-Mailer: git-send-email 2.43.0 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" X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2387; i=hyc.lee@gmail.com; h=from:subject:message-id; bh=4SkzOidhvnxWCRowJi5VGUs1BjdwjDVLRVBmyyUgQ1c=; b=owEBbQKS/ZANAwAKATTyMPr3jkjTAcsmYgBqhClU2oiZwfjcTMFenw8/lTVpUGIsotHAi3255 Z6DYh/0YYuJAjMEAAEKAB0WIQTVhSnMU3bjbW4eb2I08jD6945I0wUCaoQpVAAKCRA08jD6945I 0+SJD/4jZ2+5HVPf48AYEbSr9mfxJtEveHj+Ddz/EKgMZQjQ2xg9FrebKxzfpNBOVOhCFMI1PGC dJdi+0janHr/GpqOwUXEg9jIF2XyATVXwBbBxAn2RjFyk/sLHWjUz4nD7vC2WtS49F/IhvprTZ7 HWTPboihtIDFyuKXYyby4vj5yFtmErCNNXzNRP8SubYgc9WVY98DjtOF7bPIeCXHwL69YGgQogb nsjAQswWiZUdpYPvJXhOdh89TCad49TFXOW10q9DeEt+1NeXZmr58Rs9OfReZhzZP7g51KslBG5 tAVujweN7h6I8AFw++j58VIaBe8viByCOxSwgpRtSrmrRB9x+aSuT3Sl4hNNTgB82lqAtXOadp+ UUXhWwmi1NMq6fz8mQKLcMO5XtuvODkReI9wnVd11AtbE+fMvkzaZhZl9vjUREc5+qB+ElPvirV qShjgsBwowsgsQg5O4PQK5/Cu/gp4qLlfpUyanAbDQhrkhEETOZKne/GpxjVmYgL7RuaMtOpr9x 3MtzAzMs6ZHfjWfMwmFssRYdQqhUDsrfKzVOoSObbRE+vLX0kF+ajK0irbbQY2HTOdh+2ticIJv ABpsCGCFTNnwhdWA7+GrOn/y8yU34yPoUoYZSFA8l8gt3JC9bd10ZG7+EpgwYBZbLr1UQkrRJYs 1ExgES4vfkL+V0w== X-Developer-Key: i=hyc.lee@gmail.com; a=openpgp; fpr=D58529CC5376E36D6E1E6F6234F230FAF78E48D3 Content-Transfer-Encoding: quoted-printable The NTFS boot sector stores the MFT and MFTMirr locations as unsigned 64-bit LCNs, but parse_ntfs_boot_sector() decoded them into an s64. A crafted high-bit value could therefore become negative and pass the existing upper-bound check. The invalid value then propagated into the MFT zone allocator and could result in an out-of-bounds access to lcn_empty_bits_per_page. Fixes: 11ccc9107dc4 ("ntfs: update runlist handling and cluster allocator") Closes: https://lore.kernel.org/all/57514.1787000602@localhost Cc: stable@vger.kernel.org Signed-off-by: Hyunchul Lee --- fs/ntfs/super.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c index 8abe7bee4c0d..8a712cafe954 100644 --- a/fs/ntfs/super.c +++ b/fs/ntfs/super.c @@ -645,7 +645,7 @@ static bool parse_ntfs_boot_sector(struct ntfs_volume *= vol, { unsigned int sectors_per_cluster, sectors_per_cluster_bits, nr_hidden_sec= ts; int clusters_per_mft_record, clusters_per_index_record; - s64 ll; + u64 ll; =20 vol->sector_size =3D le16_to_cpu(b->bpb.bytes_per_sector); vol->sector_size_bits =3D ffs(vol->sector_size) - 1; @@ -755,14 +755,14 @@ static bool parse_ntfs_boot_sector(struct ntfs_volume= *vol, * the same as it is much faster on 32-bit CPUs. */ ll =3D le64_to_cpu(b->number_of_sectors) >> sectors_per_cluster_bits; - if ((u64)ll >=3D 1ULL << 32) { + if (ll >=3D 1ULL << 32) { ntfs_error(vol->sb, "Cannot handle 64-bit clusters."); return false; } vol->nr_clusters =3D ll; ntfs_debug("vol->nr_clusters =3D 0x%llx", vol->nr_clusters); ll =3D le64_to_cpu(b->mft_lcn); - if (ll >=3D vol->nr_clusters) { + if (ll >=3D (u64)vol->nr_clusters) { ntfs_error(vol->sb, "MFT LCN (%lli, 0x%llx) is beyond end of volume. We= ird.", ll, ll); return false; @@ -770,7 +770,7 @@ static bool parse_ntfs_boot_sector(struct ntfs_volume *= vol, vol->mft_lcn =3D ll; ntfs_debug("vol->mft_lcn =3D 0x%llx", vol->mft_lcn); ll =3D le64_to_cpu(b->mftmirr_lcn); - if (ll >=3D vol->nr_clusters) { + if (ll >=3D (u64)vol->nr_clusters) { ntfs_error(vol->sb, "MFTMirr LCN (%lli, 0x%llx) is beyond end of volume.= Weird.", ll, ll); return false; --- base-commit: df7dce2090342170b7643d36f694204cae7792a9 change-id: 20260818-fix-negative-mft-lcn-596257dd23c8 Best regards, --=20 Thanks, Hyunchul