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-rw-r--r--fs/char_dev.c78
1 files changed, 37 insertions, 41 deletions
diff --git a/fs/char_dev.c b/fs/char_dev.c
index a279c58fe360..d18cad28c1c3 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -88,22 +88,31 @@ static int find_dynamic_major(void)
/*
* Register a single major with a specified minor range.
*
- * If major == 0 this functions will dynamically allocate a major and return
- * its number.
- *
- * If major > 0 this function will attempt to reserve the passed range of
- * minors and will return zero on success.
+ * If major == 0 this function will dynamically allocate an unused major.
+ * If major > 0 this function will attempt to reserve the range of minors
+ * with given major.
*
- * Returns a -ve errno on failure.
*/
static struct char_device_struct *
__register_chrdev_region(unsigned int major, unsigned int baseminor,
int minorct, const char *name)
{
- struct char_device_struct *cd, **cp;
- int ret = 0;
+ struct char_device_struct *cd, *curr, *prev = NULL;
+ int ret = -EBUSY;
int i;
+ if (major >= CHRDEV_MAJOR_MAX) {
+ pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
+ name, major, CHRDEV_MAJOR_MAX-1);
+ return ERR_PTR(-EINVAL);
+ }
+
+ if (minorct > MINORMASK + 1 - baseminor) {
+ pr_err("CHRDEV \"%s\" minor range requested (%u-%u) is out of range of maximum range (%u-%u) for a single major\n",
+ name, baseminor, baseminor + minorct - 1, 0, MINORMASK);
+ return ERR_PTR(-EINVAL);
+ }
+
cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
if (cd == NULL)
return ERR_PTR(-ENOMEM);
@@ -120,10 +129,20 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
major = ret;
}
- if (major >= CHRDEV_MAJOR_MAX) {
- pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
- name, major, CHRDEV_MAJOR_MAX-1);
- ret = -EINVAL;
+ i = major_to_index(major);
+ for (curr = chrdevs[i]; curr; prev = curr, curr = curr->next) {
+ if (curr->major < major)
+ continue;
+
+ if (curr->major > major)
+ break;
+
+ if (curr->baseminor + curr->minorct <= baseminor)
+ continue;
+
+ if (curr->baseminor >= baseminor + minorct)
+ break;
+
goto out;
}
@@ -132,37 +151,14 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
cd->minorct = minorct;
strlcpy(cd->name, name, sizeof(cd->name));
- i = major_to_index(major);
-
- for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
- if ((*cp)->major > major ||
- ((*cp)->major == major &&
- (((*cp)->baseminor >= baseminor) ||
- ((*cp)->baseminor + (*cp)->minorct > baseminor))))
- break;
-
- /* Check for overlapping minor ranges. */
- if (*cp && (*cp)->major == major) {
- int old_min = (*cp)->baseminor;
- int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
- int new_min = baseminor;
- int new_max = baseminor + minorct - 1;
-
- /* New driver overlaps from the left. */
- if (new_max >= old_min && new_max <= old_max) {
- ret = -EBUSY;
- goto out;
- }
-
- /* New driver overlaps from the right. */
- if (new_min <= old_max && new_min >= old_min) {
- ret = -EBUSY;
- goto out;
- }
+ if (!prev) {
+ cd->next = curr;
+ chrdevs[i] = cd;
+ } else {
+ cd->next = prev->next;
+ prev->next = cd;
}
- cd->next = *cp;
- *cp = cd;
mutex_unlock(&chrdevs_lock);
return cd;
out: