[PATCH] radix-tree: fix memory leak in radix_tree_insert

[Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>]

[Syz report]
BUG: memory leak
unreferenced object 0xffff88810bbf56d8 (size 576):
  comm "syz-executor250", pid 5051, jiffies 4294951219 (age 12.920s)
  hex dump (first 32 bytes):
    3c 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00  <...............
    f0 a9 2d 0c 81 88 ff ff f0 56 bf 0b 81 88 ff ff  ..-......V......
  backtrace:
    [<ffffffff81631398>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
    [<ffffffff81631398>] slab_post_alloc_hook mm/slab.h:766 [inline]
    [<ffffffff81631398>] slab_alloc_node mm/slub.c:3478 [inline]
    [<ffffffff81631398>] slab_alloc mm/slub.c:3486 [inline]
    [<ffffffff81631398>] __kmem_cache_alloc_lru mm/slub.c:3493 [inline]
    [<ffffffff81631398>] kmem_cache_alloc+0x298/0x430 mm/slub.c:3502
    [<ffffffff84b5094c>] radix_tree_node_alloc.constprop.0+0x7c/0x1a0 lib/radix-tree.c:276
    [<ffffffff84b524cf>] __radix_tree_create lib/radix-tree.c:624 [inline]
    [<ffffffff84b524cf>] radix_tree_insert+0x14f/0x360 lib/radix-tree.c:712
    [<ffffffff84ae105d>] qrtr_tx_wait net/qrtr/af_qrtr.c:277 [inline]
    [<ffffffff84ae105d>] qrtr_node_enqueue+0x57d/0x630 net/qrtr/af_qrtr.c:348
    [<ffffffff84ae26f6>] qrtr_bcast_enqueue+0x66/0xd0 net/qrtr/af_qrtr.c:891
    [<ffffffff84ae32d2>] qrtr_sendmsg+0x232/0x450 net/qrtr/af_qrtr.c:992
    [<ffffffff83ec3c32>] sock_sendmsg_nosec net/socket.c:730 [inline]
    [<ffffffff83ec3c32>] __sock_sendmsg+0x52/0xa0 net/socket.c:745
    [<ffffffff83ec3d7b>] sock_write_iter+0xfb/0x180 net/socket.c:1158
    [<ffffffff816961a7>] call_write_iter include/linux/fs.h:2020 [inline]
    [<ffffffff816961a7>] new_sync_write fs/read_write.c:491 [inline]
    [<ffffffff816961a7>] vfs_write+0x327/0x590 fs/read_write.c:584
    [<ffffffff816966fb>] ksys_write+0x13b/0x170 fs/read_write.c:637
    [<ffffffff84b6ddcf>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
    [<ffffffff84b6ddcf>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
    [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b

[Analysis]
When creating child nodes, if not all child nodes used to store indexes are created,
so the child nodes created before the failure should be released.

Reported-and-tested-by: syzbot+006987d1be3586e13555@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
---
 lib/radix-tree.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index a89df8afa510..c5caf5b7523a 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -616,9 +616,10 @@ static int __radix_tree_create(struct radix_tree_root *root,
 	struct radix_tree_node *node = NULL, *child;
 	void __rcu **slot = (void __rcu **)&root->xa_head;
 	unsigned long maxindex;
-	unsigned int shift, offset = 0;
+	unsigned int shift, offset = 0, mmshift = 0;
 	unsigned long max = index;
 	gfp_t gfp = root_gfp_mask(root);
+	int ret;
 
 	shift = radix_tree_load_root(root, &child, &maxindex);
 
@@ -628,6 +629,7 @@ static int __radix_tree_create(struct radix_tree_root *root,
 		if (error < 0)
 			return error;
 		shift = error;
+		mmshift = error;
 		child = rcu_dereference_raw(root->xa_head);
 	}
 
@@ -637,8 +639,10 @@ static int __radix_tree_create(struct radix_tree_root *root,
 			/* Have to add a child node.  */
 			child = radix_tree_node_alloc(gfp, node, root, shift,
 							offset, 0, 0);
-			if (!child)
-				return -ENOMEM;
+			if (!child) {
+				 ret = -ENOMEM;
+				 goto freec;
+			}
 			rcu_assign_pointer(*slot, node_to_entry(child));
 			if (node)
 				node->count++;
@@ -656,6 +660,17 @@ static int __radix_tree_create(struct radix_tree_root *root,
 	if (slotp)
 		*slotp = slot;
 	return 0;
+freec:
+	if (mmshift > 0) {
+		struct radix_tree_node *pn;
+		while (shift < mmshift && node) {
+			pn = node->parent;
+			radix_tree_node_rcu_free(&node->rcu_head);
+			shift += RADIX_TREE_MAP_SHIFT;
+			node = pn;
+		}
+	}
+	return ret;
 }
 
 /*
-- 
2.43.0