[PATCH 4/4] media: rc: Add missing locking for keymap

When the rc_map for an rc_dev gets updated, locking is required but is
missing in places. A concurrent scancode lookup and a call to
rc_{register,unregistered}_device() could result in a use-after-free;
this could happen if IR is decoded during those function calls.

We also fix some ugliness like open-coded krealloc() and removing the
pointless alloc member of rc_map.

Add lockdep assertions where locks are required.

Fixes: dccc0c3ddf8f ("media: rc: fix race between unregister and urb/irq callbacks")
Signed-off-by: Sean Young <[email protected]>
Cc: [email protected]
---
 drivers/media/rc/rc-main.c | 122 ++++++++++++++++++++++---------------
 include/media/rc-map.h     |   2 -
 2 files changed, 74 insertions(+), 50 deletions(-)

diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c
index 10b924186826..2586e1fa0897 100644
--- a/drivers/media/rc/rc-main.c
+++ b/drivers/media/rc/rc-main.c
@@ -17,9 +17,8 @@
 #include <linux/module.h>
 #include "rc-core-priv.h"
 
-/* Sizes are in bytes, 256 bytes allows for 32 entries on x64 */
-#define IR_TAB_MIN_SIZE	256
-#define IR_TAB_MAX_SIZE	8192
+#define IR_TAB_MIN_SIZE	32
+#define IR_TAB_MAX_SIZE	1024
 
 static const struct {
 	const char *name;
@@ -105,7 +104,6 @@ static struct rc_map_list *seek_rc_map(const char *name)
 
 struct rc_map *rc_map_get(const char *name)
 {
-
 	struct rc_map_list *map;
 
 	map = seek_rc_map(name);
@@ -202,7 +200,7 @@ static int scancode_to_u64(const struct input_keymap_entry *ke, u64 *scancode)
  * ir_create_table() - initializes a scancode table
  * @dev:	the rc_dev device
  * @rc_map:	the rc_map to initialize
- * @name:	name to assign to the table
+ * @map_name:	name to assign to the table
  * @rc_proto:	ir type to assign to the new table
  * @size:	initial size of the table
  *
@@ -212,23 +210,33 @@ static int scancode_to_u64(const struct input_keymap_entry *ke, u64 *scancode)
  * return:	zero on success or a negative error code
  */
 static int ir_create_table(struct rc_dev *dev, struct rc_map *rc_map,
-			   const char *name, u64 rc_proto, size_t size)
+			   const char *map_name, u64 rc_proto, size_t size)
 {
-	rc_map->name = kstrdup(name, GFP_KERNEL);
-	if (!rc_map->name)
+	struct rc_map_table *scan;
+	unsigned int alloc;
+	char *name;
+
+	name = kstrdup(map_name, GFP_KERNEL);
+	if (!name)
 		return -ENOMEM;
-	rc_map->rc_proto = rc_proto;
-	rc_map->alloc = roundup_pow_of_two(size * sizeof(struct rc_map_table));
-	rc_map->size = rc_map->alloc / sizeof(struct rc_map_table);
-	rc_map->scan = kmalloc(rc_map->alloc, GFP_KERNEL);
-	if (!rc_map->scan) {
-		kfree(rc_map->name);
-		rc_map->name = NULL;
+
+	alloc = roundup_pow_of_two(size);
+	scan = kmalloc_objs(struct rc_map_table, alloc, GFP_KERNEL);
+	if (!scan) {
+		kfree(name);
 		return -ENOMEM;
 	}
 
-	dev_dbg(&dev->dev, "Allocated space for %u keycode entries (%u bytes)\n",
-		rc_map->size, rc_map->alloc);
+	scoped_guard(spinlock_irqsave, &dev->rc_map.lock) {
+		rc_map->name = name;
+		rc_map->scan = scan;
+		rc_map->rc_proto = rc_proto;
+		rc_map->len = 0;
+		rc_map->size = alloc;
+	}
+
+	dev_dbg(&dev->dev, "Allocated space for %u keycode entries (%zu bytes)\n",
+		rc_map->size, rc_map->size * sizeof(struct rc_map_table));
 	return 0;
 }
 
@@ -236,16 +244,26 @@ static int ir_create_table(struct rc_dev *dev, struct rc_map *rc_map,
  * ir_free_table() - frees memory allocated by a scancode table
  * @rc_map:	the table whose mappings need to be freed
  *
- * This routine will free memory alloctaed for key mappings used by given
+ * This routine will free memory allocated for key mappings used by given
  * scancode table.
  */
 static void ir_free_table(struct rc_map *rc_map)
 {
-	rc_map->size = 0;
-	kfree(rc_map->name);
-	rc_map->name = NULL;
-	kfree(rc_map->scan);
-	rc_map->scan = NULL;
+	struct rc_map_table *scan;
+	const char *name;
+
+	scoped_guard(spinlock_irqsave, &rc_map->lock) {
+		name = rc_map->name;
+		scan = rc_map->scan;
+
+		rc_map->size = 0;
+		rc_map->len = 0;
+		rc_map->name = NULL;
+		rc_map->scan = NULL;
+	}
+
+	kfree(name);
+	kfree(scan);
 }
 
 /**
@@ -262,38 +280,38 @@ static void ir_free_table(struct rc_map *rc_map)
 static int ir_resize_table(struct rc_dev *dev, struct rc_map *rc_map,
 			   gfp_t gfp_flags)
 {
-	unsigned int oldalloc = rc_map->alloc;
-	unsigned int newalloc = oldalloc;
-	struct rc_map_table *oldscan = rc_map->scan;
+	unsigned int newsize = rc_map->size;
 	struct rc_map_table *newscan;
 
+	lockdep_assert_held(&rc_map->lock);
+
 	if (rc_map->size == rc_map->len) {
 		/* All entries in use -> grow keytable */
-		if (rc_map->alloc >= IR_TAB_MAX_SIZE)
+		newsize *= 2;
+
+		if (newsize >= IR_TAB_MAX_SIZE)
 			return -ENOMEM;
 
-		newalloc *= 2;
-		dev_dbg(&dev->dev, "Growing table to %u bytes\n", newalloc);
+		dev_dbg(&dev->dev, "Growing table to %u entries\n", newsize);
 	}
 
-	if ((rc_map->len * 3 < rc_map->size) && (oldalloc > IR_TAB_MIN_SIZE)) {
+	if (rc_map->len * 3 < rc_map->size && rc_map->size > IR_TAB_MIN_SIZE) {
 		/* Less than 1/3 of entries in use -> shrink keytable */
-		newalloc /= 2;
-		dev_dbg(&dev->dev, "Shrinking table to %u bytes\n", newalloc);
+		newsize /= 2;
+		dev_dbg(&dev->dev, "Shrinking table to %u entries\n", newsize);
 	}
 
-	if (newalloc == oldalloc)
+	if (newsize == rc_map->size)
 		return 0;
 
-	newscan = kmalloc(newalloc, gfp_flags);
+	newscan = krealloc_array(rc_map->scan, newsize,
+				 sizeof(struct rc_map_table), gfp_flags);
 	if (!newscan)
 		return -ENOMEM;
 
-	memcpy(newscan, rc_map->scan, rc_map->len * sizeof(struct rc_map_table));
 	rc_map->scan = newscan;
-	rc_map->alloc = newalloc;
-	rc_map->size = rc_map->alloc / sizeof(struct rc_map_table);
-	kfree(oldscan);
+	rc_map->size = newsize;
+
 	return 0;
 }
 
@@ -318,6 +336,8 @@ static unsigned int ir_update_mapping(struct rc_dev *dev,
 	int old_keycode = rc_map->scan[index].keycode;
 	int i;
 
+	lockdep_assert_held(&rc_map->lock);
+
 	/* Did the user wish to remove the mapping? */
 	if (new_keycode == KEY_RESERVED || new_keycode == KEY_UNKNOWN) {
 		dev_dbg(&dev->dev, "#%d: Deleting scan 0x%04llx\n",
@@ -373,6 +393,8 @@ static unsigned int ir_establish_scancode(struct rc_dev *dev,
 {
 	unsigned int i;
 
+	lockdep_assert_held(&rc_map->lock);
+
 	/*
 	 * Unfortunately, some hardware-based IR decoders don't provide
 	 * all bits for the complete IR code. In general, they provide only
@@ -397,7 +419,7 @@ static unsigned int ir_establish_scancode(struct rc_dev *dev,
 	/* No previous mapping found, we might need to grow the table */
 	if (rc_map->size == rc_map->len) {
 		if (!resize || ir_resize_table(dev, rc_map, GFP_ATOMIC))
-			return -1U;
+			return UINT_MAX;
 	}
 
 	/* i is the proper index to insert our new keycode */
@@ -479,16 +501,18 @@ static int ir_setkeytable(struct rc_dev *dev, const struct rc_map *from)
 	if (rc)
 		return rc;
 
-	for (i = 0; i < from->size; i++) {
-		index = ir_establish_scancode(dev, rc_map,
-					      from->scan[i].scancode, false);
-		if (index >= rc_map->len) {
-			rc = -ENOMEM;
-			break;
-		}
+	scoped_guard(spinlock_irqsave, &dev->rc_map.lock) {
+		for (i = 0; i < from->size; i++) {
+			index = ir_establish_scancode(dev, rc_map,
+						      from->scan[i].scancode, false);
+			if (index >= rc_map->len) {
+				rc = -ENOMEM;
+				break;
+			}
 
-		ir_update_mapping(dev, rc_map, index,
-				  from->scan[i].keycode);
+			ir_update_mapping(dev, rc_map, index,
+					  from->scan[i].keycode);
+		}
 	}
 
 	if (rc)
@@ -524,6 +548,8 @@ static unsigned int ir_lookup_by_scancode(const struct rc_map *rc_map,
 {
 	struct rc_map_table *res;
 
+	lockdep_assert_held(&rc_map->lock);
+
 	res = bsearch(&scancode, rc_map->scan, rc_map->len,
 		      sizeof(struct rc_map_table), rc_map_cmp);
 	if (!res)
diff --git a/include/media/rc-map.h b/include/media/rc-map.h
index d95ed3e96de2..f167c37179c8 100644
--- a/include/media/rc-map.h
+++ b/include/media/rc-map.h
@@ -148,7 +148,6 @@ struct rc_map_table {
  * @scan: pointer to struct &rc_map_table
  * @size: Max number of entries
  * @len: Number of entries that are in use
- * @alloc: size of \*scan, in bytes
  * @rc_proto: type of the remote controller protocol, as defined at
  *	     enum &rc_proto
  * @name: name of the key map table
@@ -158,7 +157,6 @@ struct rc_map {
 	struct rc_map_table	*scan;
 	unsigned int		size;
 	unsigned int		len;
-	unsigned int		alloc;
 	enum rc_proto		rc_proto;
 	const char		*name;
 	spinlock_t		lock;
-- 
2.55.0