[PATCH] list_lru: fix memory leak in __memcg_init_list_lru_node

From: Shakeel Butt <shakeelb@google.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Michal Hocko <mhocko@suse.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Shakeel Butt <shakeelb@google.com>,
	syzbot+f90a420dfe2b1b03cb2c@syzkaller.appspotmail.com
Subject: [PATCH] list_lru: fix memory leak in __memcg_init_list_lru_node
Date: Mon, 27 May 2019 21:32:02 -0700	[thread overview]
Message-ID: <20190528043202.99980-1-shakeelb@google.com> (raw)

Syzbot reported following memory leak:

ffffffffda RBX: 0000000000000003 RCX: 0000000000441f79
BUG: memory leak
unreferenced object 0xffff888114f26040 (size 32):
  comm "syz-executor626", pid 7056, jiffies 4294948701 (age 39.410s)
  hex dump (first 32 bytes):
    40 60 f2 14 81 88 ff ff 40 60 f2 14 81 88 ff ff  @`......@`......
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<0000000018f36b56>] kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline]
    [<0000000018f36b56>] slab_post_alloc_hook mm/slab.h:439 [inline]
    [<0000000018f36b56>] slab_alloc mm/slab.c:3326 [inline]
    [<0000000018f36b56>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553
    [<0000000055b9a1a5>] kmalloc include/linux/slab.h:547 [inline]
    [<0000000055b9a1a5>] __memcg_init_list_lru_node+0x58/0xf0 mm/list_lru.c:352
    [<000000001356631d>] memcg_init_list_lru_node mm/list_lru.c:375 [inline]
    [<000000001356631d>] memcg_init_list_lru mm/list_lru.c:459 [inline]
    [<000000001356631d>] __list_lru_init+0x193/0x2a0 mm/list_lru.c:626
    [<00000000ce062da3>] alloc_super+0x2e0/0x310 fs/super.c:269
    [<000000009023adcf>] sget_userns+0x94/0x2a0 fs/super.c:609
    [<0000000052182cd8>] sget+0x8d/0xb0 fs/super.c:660
    [<0000000006c24238>] mount_nodev+0x31/0xb0 fs/super.c:1387
    [<0000000006016a76>] fuse_mount+0x2d/0x40 fs/fuse/inode.c:1236
    [<000000009a61ec1d>] legacy_get_tree+0x27/0x80 fs/fs_context.c:661
    [<0000000096cd9ef8>] vfs_get_tree+0x2e/0x120 fs/super.c:1476
    [<000000005b8f472d>] do_new_mount fs/namespace.c:2790 [inline]
    [<000000005b8f472d>] do_mount+0x932/0xc50 fs/namespace.c:3110
    [<00000000afb009b4>] ksys_mount+0xab/0x120 fs/namespace.c:3319
    [<0000000018f8c8ee>] __do_sys_mount fs/namespace.c:3333 [inline]
    [<0000000018f8c8ee>] __se_sys_mount fs/namespace.c:3330 [inline]
    [<0000000018f8c8ee>] __x64_sys_mount+0x26/0x30 fs/namespace.c:3330
    [<00000000f42066da>] do_syscall_64+0x76/0x1a0 arch/x86/entry/common.c:301
    [<0000000043d74ca0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

This is a simple off by one bug on the error path.

Reported-by: syzbot+f90a420dfe2b1b03cb2c@syzkaller.appspotmail.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
---
 mm/list_lru.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 0bdf3152735e..92870be4a322 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -358,7 +358,7 @@ static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
 	}
 	return 0;
 fail:
-	__memcg_destroy_list_lru_node(memcg_lrus, begin, i - 1);
+	__memcg_destroy_list_lru_node(memcg_lrus, begin, i);
 	return -ENOMEM;
 }
 
-- 
2.22.0.rc1.257.g3120a18244-goog

