Not only is this helpful for debugging, it also saves the caller an
ioctl in the case where a device should be used if it exists or created
otherwise. To ensure existing userspace is not broken, this feature is
only enabled in strict mode.
Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-ioctl.c | 31 +++++++++++++++++++++++++------
include/uapi/linux/dm-ioctl.h | 4 ++--
2 files changed, 27 insertions(+), 8 deletions(-)
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 7eab9a8c77ff3286346a1c44581d3b6370a731eb..4eb3eda2fe169f64259458dd678833f444d76ce0 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -259,11 +259,14 @@ static void free_cell(struct hash_cell *hc)
}
}
+static void __dev_status(struct mapped_device *md, struct dm_ioctl *param);
+
/*
* The kdev_t and uuid of a device can never change once it is
* initially inserted.
*/
-static int dm_hash_insert(const char *name, const char *uuid, struct mapped_device *md)
+static int dm_hash_insert(const char *name, const char *uuid, struct mapped_device *md,
+ struct dm_ioctl *param)
{
struct hash_cell *cell, *hc;
@@ -280,6 +283,8 @@ static int dm_hash_insert(const char *name, const char *uuid, struct mapped_devi
down_write(&_hash_lock);
hc = __get_name_cell(name);
if (hc) {
+ if (param)
+ __dev_status(hc->md, param);
dm_put(hc->md);
goto bad;
}
@@ -290,6 +295,8 @@ static int dm_hash_insert(const char *name, const char *uuid, struct mapped_devi
hc = __get_uuid_cell(uuid);
if (hc) {
__unlink_name(cell);
+ if (param)
+ __dev_status(hc->md, param);
dm_put(hc->md);
goto bad;
}
@@ -901,10 +908,12 @@ static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_si
m = MINOR(huge_decode_dev(param->dev));
r = dm_create(m, &md, param->flags & DM_DISABLE_UEVENTS_FLAG);
- if (r)
+ if (r) {
+ DMERR("Could not create device-mapper device");
return r;
+ }
- r = dm_hash_insert(param->name, *param->uuid ? param->uuid : NULL, md);
+ r = dm_hash_insert(param->name, *param->uuid ? param->uuid : NULL, md, param);
if (r) {
dm_put(md);
dm_destroy(md);
@@ -2234,6 +2243,7 @@ static int ctl_ioctl(struct file *file, uint command, struct dm_ioctl __user *us
int ioctl_flags;
int param_flags;
unsigned int cmd;
+ bool do_copy;
struct dm_ioctl *param;
ioctl_fn fn = NULL;
size_t input_param_size;
@@ -2307,9 +2317,18 @@ static int ctl_ioctl(struct file *file, uint command, struct dm_ioctl __user *us
param->flags |= old_flags;
/*
- * Copy the results back to userland.
+ * Copy the results back to userland if either:
+ *
+ * - The ioctl succeeded.
+ * - The ioctl is DM_DEV_CREATE, the return value is -EBUSY,
+ * and strict parameter checking is enabled.
*/
- if (!r && copy_to_user(user, param, param->data_size))
+ do_copy = r == 0;
+ if (r == -EBUSY && !sloppy_checks(param) && cmd == DM_DEV_CREATE_CMD) {
+ param->flags |= DM_EXISTS_FLAG;
+ do_copy = true;
+ }
+ if (do_copy && copy_to_user(user, param, param->data_size))
r = -EFAULT;
out:
@@ -2488,7 +2507,7 @@ int __init dm_early_create(struct dm_ioctl *dmi,
return r;
/* hash insert */
- r = dm_hash_insert(dmi->name, *dmi->uuid ? dmi->uuid : NULL, md);
+ r = dm_hash_insert(dmi->name, *dmi->uuid ? dmi->uuid : NULL, md, NULL);
if (r)
goto err_destroy_dm;
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index b338a4f9a299acda9430995d63fbb490e70c8cd8..195d60be4aba4f20b7220b900c87d6d3a86014a2 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -344,8 +344,8 @@ enum {
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */
#define DM_SUSPEND_FLAG (1 << 1) /* In/Out */
-#define DM_EXISTS_FLAG (1 << 2) /* Not used by kernel, reserved for
- * libdevmapper in userland
+#define DM_EXISTS_FLAG (1 << 2) /* Set when trying to create a
+ * device that already exists
*/
#define DM_PERSISTENT_DEV_FLAG (1 << 3) /* In */
--
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
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