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Tue, 30 May 2023 16:31:56 -0400 (EDT) From: Demi Marie Obenour To: Jens Axboe , =?utf-8?q?Roger_Pau_Monn=C3=A9?= , Alasdair Kergon , Mike Snitzer , dm-devel@redhat.com Cc: Demi Marie Obenour , =?utf-8?q?Marek_Marczy?= =?utf-8?q?kowski-G=C3=B3recki?= , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org Subject: [PATCH v2 08/16] device-mapper: Allow userspace to provide expected diskseq Date: Tue, 30 May 2023 16:31:08 -0400 Message-Id: <20230530203116.2008-9-demi@invisiblethingslab.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230530203116.2008-1-demi@invisiblethingslab.com> References: <20230530203116.2008-1-demi@invisiblethingslab.com> MIME-Version: 1.0 X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS, SPF_NONE,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1767353733299530581?= X-GMAIL-MSGID: =?utf-8?q?1767353733299530581?= This can be used to avoid race conditions in which a device is destroyed and recreated with the same major/minor, name, or UUID. diskseqs are only honored if strict parameter checking is on, to avoid any risk of breaking old userspace. Signed-off-by: Demi Marie Obenour --- drivers/md/dm-ioctl.c | 48 ++++++++++++++++++++++++++++------- include/uapi/linux/dm-ioctl.h | 33 +++++++++++++++++++++--- 2 files changed, 69 insertions(+), 12 deletions(-) diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index cf752e72ef6a2d8f8230e5bd6d1a6dc817a4f597..01cdf57bcafbf7f3e1b8304eec28792c6b24642d 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -871,6 +871,9 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param) } dm_put_live_table(md, srcu_idx); } + + if (param->version[0] >= DM_VERSION_MAJOR_STRICT) + dm_set_diskseq(param, disk->diskseq); } static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_size) @@ -889,6 +892,8 @@ static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_si if (r) return r; + param->flags &= ~DM_INACTIVE_PRESENT_FLAG; + r = dm_hash_insert(param->name, *param->uuid ? param->uuid : NULL, md); if (r) { dm_put(md); @@ -909,6 +914,7 @@ static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_si static struct hash_cell *__find_device_hash_cell(struct dm_ioctl *param) { struct hash_cell *hc = NULL; + static_assert(offsetof(struct dm_ioctl, diskseq_high) == offsetof(struct dm_ioctl, data) + 3); if (*param->uuid) { if (*param->name || param->dev) { @@ -937,6 +943,27 @@ static struct hash_cell *__find_device_hash_cell(struct dm_ioctl *param) } else return NULL; + if (param->version[0] >= DM_VERSION_MAJOR_STRICT) { + u64 expected_diskseq = dm_get_diskseq(param); + u64 diskseq; + struct mapped_device *md = hc->md; + + if (WARN_ON_ONCE(md->disk == NULL)) + return NULL; + diskseq = md->disk->diskseq; + if (WARN_ON_ONCE(diskseq == 0)) + return NULL; + if (expected_diskseq != 0) { + if (expected_diskseq != diskseq) { + DMERR("Diskseq mismatch: expected %llu actual %llu", + expected_diskseq, diskseq); + return NULL; + } + } else { + dm_set_diskseq(param, diskseq); + } + } + /* * Sneakily write in both the name and the uuid * while we have the cell. @@ -2088,7 +2115,6 @@ static int validate_params(uint cmd, struct dm_ioctl *param, uint32_t ioctl_flags, uint32_t supported_flags) { static_assert(__same_type(param->flags, supported_flags)); - u64 zero = 0; if (cmd == DM_DEV_CREATE_CMD) { if (!*param->name) { @@ -2112,14 +2138,24 @@ static int validate_params(uint cmd, struct dm_ioctl *param, return 0; } + if (param->data_size < sizeof(struct dm_ioctl)) { + DMERR("Entire struct dm_ioctl (size %zu) must be valid, but only %u was valid", + sizeof(struct dm_ioctl), param->data_size); + return -EINVAL; + } + /* Check that strings are terminated */ if (!no_non_nul_after_nul(param->name, DM_NAME_LEN, cmd, "Name") || !no_non_nul_after_nul(param->uuid, DM_UUID_LEN, cmd, "UUID")) { return -EINVAL; } - if (memcmp(param->data, &zero, sizeof(param->data)) != 0) { - DMERR("second padding field not zeroed in strict mode (cmd %u)", cmd); + /* + * This also reads the NUL terminator of the UUID, but that has already been + * checked to be zero by no_non_nul_after_nul(). + */ + if (*(const u32 *)((const char *)param + sizeof(struct dm_ioctl) - 8) != 0) { + DMERR("padding field not zeroed in strict mode (cmd %u)", cmd); return -EINVAL; } @@ -2129,12 +2165,6 @@ static int validate_params(uint cmd, struct dm_ioctl *param, return -EINVAL; } - if (param->padding) { - DMERR("padding not zeroed in strict mode (got %u, cmd %u)", - param->padding, cmd); - return -EINVAL; - } - if (param->open_count != 0) { DMERR("open_count not zeroed in strict mode (got %d, cmd %u)", param->open_count, cmd); diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index 81103e1dcdac3015204e9c05d73037191e965d59..5647b218f24b626f5c1cefe8bec18dc04373c3d0 100644 --- a/include/uapi/linux/dm-ioctl.h +++ b/include/uapi/linux/dm-ioctl.h @@ -136,16 +136,43 @@ struct dm_ioctl { * For output, the ioctls return the event number, not the cookie. */ __u32 event_nr; /* in/out */ - __u32 padding; + + union { + /* valid if DM_VERSION_MAJOR is used */ + __u32 padding; /* padding */ + /* valid if DM_VERSION_MAJOR_STRICT is used */ + __u32 diskseq_low; /* in/out: low 4 bytes of the diskseq */ + }; __u64 dev; /* in/out */ char name[DM_NAME_LEN]; /* device name */ char uuid[DM_UUID_LEN]; /* unique identifier for * the block device */ - char data[7]; /* padding or data */ + union { + /* valid if DM_VERSION_MAJOR is used */ + char data[7]; /* padding or data */ + /* valid if DM_VERSION_MAJOR_STRICT is used */ + struct { + char _padding[3]; /* padding */ + __u32 diskseq_high; /* in/out: high 4 bytes of the diskseq */ + } __attribute__((packed)); + }; }; +__attribute__((always_inline)) static inline __u64 +dm_get_diskseq(const struct dm_ioctl *_i) +{ + return (__u64)_i->diskseq_high << 32 | (__u64)_i->diskseq_low; +} + +__attribute__((always_inline)) static inline void +dm_set_diskseq(struct dm_ioctl *_i, __u64 _diskseq) +{ + _i->diskseq_low = (__u32)(_diskseq & 0xFFFFFFFFU); + _i->diskseq_high = (__u32)(_diskseq >> 32); +} + /* * Used to specify tables. These structures appear after the * dm_ioctl. @@ -402,6 +429,6 @@ enum { * If DM_VERSION_MAJOR_STRICT is used, these flags are reserved and * must be zeroed. */ -#define DM_STRICT_ONLY_FLAGS ((__u32)0xFFF00004) +#define DM_STRICT_ONLY_FLAGS ((__u32)(~((1UL << 19) - 1) | 1 << 9 | 1 << 7)) #endif /* _LINUX_DM_IOCTL_H */