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[122.107.196.14]) by smtp.gmail.com with ESMTPSA id 63-20020a621542000000b00525204224afsm20014171pfv.94.2022.07.03.17.02.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 Jul 2022 17:02:36 -0700 (PDT) From: Daniil Lunev To: Alasdair Kergon Cc: Brian Geffon , Daniil Lunev , Mike Snitzer , dm-devel@redhat.com, linux-kernel@vger.kernel.org Subject: [PATCH 1/1] dm: add message command to disallow device open Date: Mon, 4 Jul 2022 10:02:25 +1000 Message-Id: <20220704100221.1.I15b3f7a84ba5a97fde9276648e391b54957103ff@changeid> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20220704000225.345536-1-dlunev@chromium.org> References: <20220704000225.345536-1-dlunev@chromium.org> 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" A message can be passed to device mapper to prohibit open on a certain mapped device. This makes possible to disallow userspace access to raw swapped data if the system uses device mapper to encrypt it at rest. Signed-off-by: Daniil Lunev --- drivers/md/dm-core.h | 1 + drivers/md/dm-ioctl.c | 10 ++++++++++ drivers/md/dm.c | 12 ++++++++++++ drivers/md/dm.h | 10 ++++++++++ include/uapi/linux/dm-ioctl.h | 5 +++++ 5 files changed, 38 insertions(+) diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h index 4277853c75351..37529b605b7c4 100644 --- a/drivers/md/dm-core.h +++ b/drivers/md/dm-core.h @@ -140,6 +140,7 @@ struct mapped_device { #define DMF_SUSPENDED_INTERNALLY 7 #define DMF_POST_SUSPENDING 8 #define DMF_EMULATE_ZONE_APPEND 9 +#define DMF_DISALLOW_OPEN 10 =20 void disable_discard(struct mapped_device *md); void disable_write_zeroes(struct mapped_device *md); diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 87310fceb0d86..e35d560aa2ff3 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -815,6 +815,9 @@ static void __dev_status(struct mapped_device *md, stru= ct dm_ioctl *param) if (dm_test_deferred_remove_flag(md)) param->flags |=3D DM_DEFERRED_REMOVE; =20 + if (dm_test_disallow_open_flag(md)) + param->flags |=3D DM_DISALLOWED_OPEN; + param->dev =3D huge_encode_dev(disk_devt(disk)); =20 /* @@ -1656,6 +1659,13 @@ static int message_for_md(struct mapped_device *md, = unsigned argc, char **argv, } return dm_cancel_deferred_remove(md); } + if (!strcasecmp(argv[0], "@disallow_open")) { + if (argc !=3D 1) { + DMERR("Invalid arguments for @disallow_open"); + return -EINVAL; + } + return dm_disallow_open(md); + } =20 r =3D dm_stats_message(md, argc, argv, result, maxlen); if (r < 2) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 82957bd460e89..3e53d1bd40f0c 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -327,6 +327,7 @@ static int dm_blk_open(struct block_device *bdev, fmode= _t mode) goto out; =20 if (test_bit(DMF_FREEING, &md->flags) || + test_bit(DMF_DISALLOW_OPEN, &md->flags) || dm_deleting_md(md)) { md =3D NULL; goto out; @@ -403,6 +404,12 @@ int dm_cancel_deferred_remove(struct mapped_device *md) return r; } =20 +int dm_disallow_open(struct mapped_device *md) +{ + set_bit(DMF_DISALLOW_OPEN, &md->flags); + return 0; +} + static void do_deferred_remove(struct work_struct *w) { dm_deferred_remove(); @@ -2883,6 +2890,11 @@ int dm_test_deferred_remove_flag(struct mapped_devic= e *md) return test_bit(DMF_DEFERRED_REMOVE, &md->flags); } =20 +int dm_test_disallow_open_flag(struct mapped_device *md) +{ + return test_bit(DMF_DISALLOW_OPEN, &md->flags); +} + int dm_suspended(struct dm_target *ti) { return dm_suspended_md(ti->table->md); diff --git a/drivers/md/dm.h b/drivers/md/dm.h index 9013dc1a7b002..da27f9dfe1413 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -163,6 +163,16 @@ int dm_test_deferred_remove_flag(struct mapped_device = *md); */ void dm_deferred_remove(void); =20 +/* + * Test if the device is openable. + */ +int dm_test_disallow_open_flag(struct mapped_device *md); + +/* + * Prevent new open request on the device. + */ +int dm_disallow_open(struct mapped_device *md); + /* * The device-mapper can be driven through one of two interfaces; * ioctl or filesystem, depending which patch you have applied. diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index 2e9550fef90fa..3b4d12d09c005 100644 --- a/include/uapi/linux/dm-ioctl.h +++ b/include/uapi/linux/dm-ioctl.h @@ -382,4 +382,9 @@ enum { */ #define DM_IMA_MEASUREMENT_FLAG (1 << 19) /* In */ =20 +/* + * If set, the device can not be opened. + */ +#define DM_DISALLOWED_OPEN (1 << 20) /* Out */ + #endif /* _LINUX_DM_IOCTL_H */ --=20 2.31.0