[v2,2/4] dm ioctl: Allow userspace to provide expected diskseq

Message ID	20230624230950.2272-3-demi@invisiblethingslab.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <dm-devel-bounces@redhat.com> Feedback-ID: iac594737:Fastmail From: Demi Marie Obenour <demi@invisiblethingslab.com> To: Alasdair Kergon <agk@redhat.com>, Mike Snitzer <snitzer@kernel.org>, dm-devel@redhat.com Date: Sat, 24 Jun 2023 19:09:45 -0400 Message-ID: <20230624230950.2272-3-demi@invisiblethingslab.com> In-Reply-To: <20230624230950.2272-1-demi@invisiblethingslab.com> References: <20230624230950.2272-1-demi@invisiblethingslab.com> MIME-Version: 1.0 X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false Subject: [dm-devel] [PATCH v2 2/4] dm ioctl: Allow userspace to provide expected diskseq Precedence: list Cc: Demi Marie Obenour <demi@invisiblethingslab.com>, linux-kernel@vger.kernel.org Errors-To: dm-devel-bounces@redhat.com Sender: "dm-devel" <dm-devel-bounces@redhat.com> Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit
Series	Diskseq support in device-mapper \| expand [v2,0/4] Diskseq support in device-mapper [v2,1/4] dm ioctl: Allow userspace to opt-in to strict parameter checks [v2,2/4] dm ioctl: Allow userspace to provide expected diskseq [v2,3/4] dm ioctl: Allow userspace to suppress uevent generation [v2,4/4] dm ioctl: inform caller about already-existing device

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index e7693479c0cd974ddde69b3b1c4c67abc2ae3ad6..7abaeec33f1884d4588e8563fb02e9ea1a6782c8 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -878,6 +878,9 @@ 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) @@ -918,6 +921,9 @@ 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, + "diskseq_high field misplaced"); if (*param->uuid) { if (*param->name || param->dev) { @@ -946,6 +952,27 @@ 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. @@ -2139,6 +2166,12 @@ 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")) @@ -2148,7 +2181,7 @@ static int validate_params(uint cmd, struct dm_ioctl *param, * This also checks the last byte of the UUID field, but that was * checked to be zero above. */ - if (*(const u64 *)((const char *)param + (sizeof(*param) - 8)) != 0) { + if (*(const u32 *)((const char *)param + (sizeof(*param) - 8)) != 0) { DMERR("second padding field not zeroed in strict mode (cmd %u)", cmd); return -EINVAL; } @@ -2159,12 +2192,6 @@ static int validate_params(uint cmd, struct dm_ioctl *param, return -EINVAL; } - if (param->padding != 0) { - 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 62bfdc95ebccb2f1c20c24496a449fe3e2a76113..1d33109aece2ff9854e752066baa96fdf7d85857 100644 --- a/include/uapi/linux/dm-ioctl.h +++ b/include/uapi/linux/dm-ioctl.h @@ -146,16 +146,43 @@ 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, must be zero in strict mode */ + 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, must be zeroed */ + __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.

[v2,2/4] dm ioctl: Allow userspace to provide expected diskseq

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