Re: [dm-devel] [PATCH v2 3/4] dm ioctl: Allow userspace to suppress uevent generation
From: Milan Broz
Date: Sun Jun 25 2023 - 09:35:04 EST
On 6/25/23 01:09, Demi Marie Obenour wrote:
Userspace can use this to avoid spamming udev with events that udev
should ignore.
Well, does it also mean that udev will not create /dev/disk/by-* symlinks
(as response to the change udev event followed by internal udev blkid scan)?
If it is a private device, that is ok. But for a visible device I think
that it breaks some assumptions in userspace (presence of symlinks mentioned
above etc).
So, what is the exact use for this patch?
Milan
Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-core.h | 2 +
drivers/md/dm-ioctl.c | 71 ++++++++++++++++++-----------------
drivers/md/dm.c | 5 ++-
include/linux/device-mapper.h | 2 +-
include/uapi/linux/dm-ioctl.h | 14 +++++--
5 files changed, 54 insertions(+), 40 deletions(-)
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 0d93661f88d306e0d0aa3a1ac085880a8b63d9d6..5a4acdbf119f9b3f9a1c60de36d23f0658449701 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -115,6 +115,8 @@ struct mapped_device {
/* for blk-mq request-based DM support */
bool init_tio_pdu:1;
+ /* If set, do not emit any uevents. */
+ bool disable_uevents:1;
struct blk_mq_tag_set *tag_set;
struct dm_stats stats;
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 7abaeec33f1884d4588e8563fb02e9ea1a6782c8..7eab9a8c77ff3286346a1c44581d3b6370a731eb 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -821,6 +821,11 @@ static struct dm_table *dm_get_live_or_inactive_table(struct mapped_device *md,
dm_get_inactive_table(md, srcu_idx) : dm_get_live_table(md, srcu_idx);
}
+static inline bool sloppy_checks(const struct dm_ioctl *param)
+{
+ return param->version[0] < DM_VERSION_MAJOR_STRICT;
+}
+
/*
* Fills in a dm_ioctl structure, ready for sending back to
* userland.
@@ -879,7 +884,7 @@ 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)
+ if (!sloppy_checks(param))
dm_set_diskseq(param, disk->diskseq);
}
@@ -895,7 +900,7 @@ static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_si
if (param->flags & DM_PERSISTENT_DEV_FLAG)
m = MINOR(huge_decode_dev(param->dev));
- r = dm_create(m, &md);
+ r = dm_create(m, &md, param->flags & DM_DISABLE_UEVENTS_FLAG);
if (r)
return r;
@@ -1463,11 +1468,6 @@ static int next_target(struct dm_target_spec *last, uint32_t next, const char *e
return 0;
}
-static inline bool sloppy_checks(const struct dm_ioctl *param)
-{
- return param->version[0] < DM_VERSION_MAJOR_STRICT;
-}
-
static bool no_non_nul_after_nul(const char *untrusted_str, size_t size,
unsigned int cmd, const char *msg)
{
@@ -1939,64 +1939,67 @@ static int target_message(struct file *filp, struct dm_ioctl *param, size_t para
* Implementation of open/close/ioctl on the special char device.
*---------------------------------------------------------------
*/
-static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags, uint32_t *supported_flags)
+static ioctl_fn lookup_ioctl(unsigned int cmd, bool strict, int *ioctl_flags,
+ uint32_t *supported_flags)
{
static const struct {
int cmd;
int flags;
ioctl_fn fn;
uint32_t supported_flags;
+ uint32_t strict_flags;
} _ioctls[] = {
/* Macro to make the structure initializers somewhat readable */
-#define I(cmd, flags, fn, supported_flags) ((typeof(_ioctls[0])) { \
+#define I(cmd, flags, fn, supported_flags, strict_flags) ((typeof(_ioctls[0])) { \
(cmd), \
(flags), \
(fn), \
/*
* Supported flags in sloppy mode must not include anything in DM_STRICT_ONLY_FLAGS.
- * Use BUILD_BUG_ON_ZERO to check for that. Currently there are no strict-only flags
- * defined.
+ * Use BUILD_BUG_ON_ZERO to check for that.
*/ \
(supported_flags) | BUILD_BUG_ON_ZERO((supported_flags) & DM_STRICT_ONLY_FLAGS), \
+ (strict_flags) | (supported_flags) | \
+ BUILD_BUG_ON_ZERO((supported_flags) & (strict_flags)), \
})
- I(DM_VERSION_CMD, 0, NULL, 0), /* version is dealt with elsewhere */
+ I(DM_VERSION_CMD, 0, NULL, 0, 0), /* version is dealt with elsewhere */
I(DM_REMOVE_ALL_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT,
- remove_all, DM_DEFERRED_REMOVE),
- I(DM_LIST_DEVICES_CMD, 0, list_devices, DM_UUID_FLAG),
+ remove_all, DM_DEFERRED_REMOVE, 0),
+ I(DM_LIST_DEVICES_CMD, 0, list_devices, DM_UUID_FLAG, 0),
I(DM_DEV_CREATE_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT,
- dev_create, DM_PERSISTENT_DEV_FLAG),
+ dev_create, DM_PERSISTENT_DEV_FLAG, DM_DISABLE_UEVENTS_FLAG),
I(DM_DEV_REMOVE_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT,
- dev_remove, DM_DEFERRED_REMOVE),
+ dev_remove, DM_DEFERRED_REMOVE, 0),
I(DM_DEV_RENAME_CMD, IOCTL_FLAGS_ISSUE_GLOBAL_EVENT, dev_rename,
- DM_QUERY_INACTIVE_TABLE_FLAG | DM_UUID_FLAG),
+ DM_QUERY_INACTIVE_TABLE_FLAG | DM_UUID_FLAG, 0),
I(DM_DEV_SUSPEND_CMD, IOCTL_FLAGS_NO_PARAMS, dev_suspend,
- DM_QUERY_INACTIVE_TABLE_FLAG | DM_SUSPEND_FLAG | DM_SKIP_LOCKFS_FLAG |
- DM_NOFLUSH_FLAG),
+ DM_QUERY_INACTIVE_TABLE_FLAG | DM_SUSPEND_FLAG |
+ DM_SKIP_LOCKFS_FLAG | DM_NOFLUSH_FLAG, 0),
I(DM_DEV_STATUS_CMD, IOCTL_FLAGS_NO_PARAMS, dev_status,
- DM_QUERY_INACTIVE_TABLE_FLAG),
+ DM_QUERY_INACTIVE_TABLE_FLAG, 0),
I(DM_DEV_WAIT_CMD, IOCTL_FLAGS_TAKES_EVENT_NR, dev_wait,
- DM_QUERY_INACTIVE_TABLE_FLAG | DM_STATUS_TABLE_FLAG | DM_NOFLUSH_FLAG),
- I(DM_TABLE_LOAD_CMD, 0, table_load, DM_QUERY_INACTIVE_TABLE_FLAG |
- DM_READONLY_FLAG),
+ DM_QUERY_INACTIVE_TABLE_FLAG | DM_STATUS_TABLE_FLAG | DM_NOFLUSH_FLAG, 0),
+ I(DM_TABLE_LOAD_CMD, 0, table_load,
+ DM_QUERY_INACTIVE_TABLE_FLAG | DM_READONLY_FLAG, 0),
I(DM_TABLE_CLEAR_CMD, IOCTL_FLAGS_NO_PARAMS, table_clear,
- DM_QUERY_INACTIVE_TABLE_FLAG),
- I(DM_TABLE_DEPS_CMD, 0, table_deps, DM_QUERY_INACTIVE_TABLE_FLAG),
+ DM_QUERY_INACTIVE_TABLE_FLAG, 0),
+ I(DM_TABLE_DEPS_CMD, 0, table_deps, DM_QUERY_INACTIVE_TABLE_FLAG, 0),
I(DM_TABLE_STATUS_CMD, 0, table_status,
- DM_QUERY_INACTIVE_TABLE_FLAG | DM_STATUS_TABLE_FLAG | DM_NOFLUSH_FLAG),
+ DM_QUERY_INACTIVE_TABLE_FLAG | DM_STATUS_TABLE_FLAG | DM_NOFLUSH_FLAG, 0),
- I(DM_LIST_VERSIONS_CMD, 0, list_versions, 0),
+ I(DM_LIST_VERSIONS_CMD, 0, list_versions, 0, 0),
- I(DM_TARGET_MSG_CMD, 0, target_message, DM_QUERY_INACTIVE_TABLE_FLAG),
- I(DM_DEV_SET_GEOMETRY_CMD, 0, dev_set_geometry, 0),
- I(DM_DEV_ARM_POLL_CMD, IOCTL_FLAGS_NO_PARAMS, dev_arm_poll, 0),
- I(DM_GET_TARGET_VERSION_CMD, 0, get_target_version, 0),
+ I(DM_TARGET_MSG_CMD, 0, target_message, DM_QUERY_INACTIVE_TABLE_FLAG, 0),
+ I(DM_DEV_SET_GEOMETRY_CMD, 0, dev_set_geometry, 0, 0),
+ I(DM_DEV_ARM_POLL_CMD, IOCTL_FLAGS_NO_PARAMS, dev_arm_poll, 0, 0),
+ I(DM_GET_TARGET_VERSION_CMD, 0, get_target_version, 0, 0),
};
if (unlikely(cmd >= ARRAY_SIZE(_ioctls)))
return NULL;
cmd = array_index_nospec(cmd, ARRAY_SIZE(_ioctls));
- *supported_flags = _ioctls[cmd].supported_flags;
+ *supported_flags = strict ? _ioctls[cmd].strict_flags : _ioctls[cmd].supported_flags;
*ioctl_flags = _ioctls[cmd].flags;
return _ioctls[cmd].fn;
}
@@ -2260,7 +2263,7 @@ static int ctl_ioctl(struct file *file, uint command, struct dm_ioctl __user *us
if (cmd == DM_VERSION_CMD)
return 0;
- fn = lookup_ioctl(cmd, &ioctl_flags, &supported_flags);
+ fn = lookup_ioctl(cmd, !sloppy_checks(¶m_kernel), &ioctl_flags, &supported_flags);
if (!fn) {
DMERR("dm_ctl_ioctl: unknown command 0x%x", command);
return -ENOTTY;
@@ -2480,7 +2483,7 @@ int __init dm_early_create(struct dm_ioctl *dmi,
m = MINOR(huge_decode_dev(dmi->dev));
/* alloc dm device */
- r = dm_create(m, &md);
+ r = dm_create(m, &md, false);
if (r)
return r;
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ea1671c39ba131ab2e49b93289d1094cda5cfb25..b7817b4aea52033afeeea9f2b93b9215de682e9c 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2281,13 +2281,14 @@ static struct dm_table *__unbind(struct mapped_device *md)
/*
* Constructor for a new device.
*/
-int dm_create(int minor, struct mapped_device **result)
+int dm_create(int minor, struct mapped_device **result, bool disable_uevents)
{
struct mapped_device *md;
md = alloc_dev(minor);
if (!md)
return -ENXIO;
+ md->disable_uevents = disable_uevents;
dm_ima_reset_data(md);
@@ -3005,6 +3006,8 @@ int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
char udev_cookie[DM_COOKIE_LENGTH];
char *envp[3] = { NULL, NULL, NULL };
char **envpp = envp;
+ if (md->disable_uevents)
+ return 0;
if (cookie) {
snprintf(udev_cookie, DM_COOKIE_LENGTH, "%s=%u",
DM_COOKIE_ENV_VAR_NAME, cookie);
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 69d0435c7ebb0d7b712e2b8bf32d9ba34c54e09e..2be940c2c6f42ed8e13b97ea8b07d0895566f3e2 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -461,7 +461,7 @@ void dm_consume_args(struct dm_arg_set *as, unsigned int num_args);
* DM_ANY_MINOR chooses the next available minor number.
*/
#define DM_ANY_MINOR (-1)
-int dm_create(int minor, struct mapped_device **md);
+int dm_create(int minor, struct mapped_device **md, bool disable_uevents);
/*
* Reference counting for md.
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 1d33109aece2ff9854e752066baa96fdf7d85857..b338a4f9a299acda9430995d63fbb490e70c8cd8 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -369,8 +369,16 @@ enum {
#define DM_BUFFER_FULL_FLAG (1 << 8) /* Out */
/*
- * This flag is now ignored if DM_VERSION_MAJOR is used, and causes
- * -EINVAL if DM_VERSION_MAJOR_STRICT is used.
+ * This flag is only recognized when DM_VERSION_MAJOR_STRICT is used.
+ * It tells the kernel to not generate any uevents for the newly-created
+ * device. Using it outside of DM_DEV_CREATE results in -EINVAL. When
+ * DM_VERSION_MAJOR is used this flag is ignored.
+ */
+#define DM_DISABLE_UEVENTS_FLAG (1 << 9) /* In */
+
+/*
+ * This flag is now ignored if DM_VERSION_MAJOR is used. When
+ * DM_VERSION_MAJOR_STRICT is used it is an alias for DM_DISABLE_UEVENT_FLAG.
*/
#define DM_SKIP_BDGET_FLAG (1 << 9) /* In */
@@ -439,8 +447,6 @@ enum {
/*
* If DM_VERSION_MAJOR is used, these flags are ignored by the kernel.
- * If DM_VERSION_MAJOR_STRICT is used, these flags are reserved and
- * must be zeroed.
*/
#define DM_STRICT_ONLY_FLAGS \
(DM_ACTIVE_PRESENT_FLAG | DM_INACTIVE_PRESENT_FLAG | \