From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by kanga.kvack.org (Postfix) with ESMTP id 01BEA8E0001 for ; Fri, 11 Jan 2019 11:52:13 -0500 (EST) Received: by mail-qk1-f199.google.com with SMTP id z68so9857836qkb.14 for ; Fri, 11 Jan 2019 08:52:12 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id s10sor70380800qvs.25.2019.01.11.08.52.11 for (Google Transport Security); Fri, 11 Jan 2019 08:52:11 -0800 (PST) From: Qian Cai Subject: [PATCH] rbtree: fix the red root Date: Fri, 11 Jan 2019 11:51:45 -0500 Message-Id: <20190111165145.23628-1-cai@lca.pw> In-Reply-To: References: Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: esploit@protonmail.ch, jejb@linux.ibm.com, dgilbert@interlog.com, martin.petersen@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai A GFP was reported, kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] SMP KASAN kasan_die_handler.cold.22+0x11/0x31 notifier_call_chain+0x17b/0x390 atomic_notifier_call_chain+0xa7/0x1b0 notify_die+0x1be/0x2e0 do_general_protection+0x13e/0x330 general_protection+0x1e/0x30 rb_insert_color+0x189/0x1480 create_object+0x785/0xca0 kmemleak_alloc+0x2f/0x50 kmem_cache_alloc+0x1b9/0x3c0 getname_flags+0xdb/0x5d0 getname+0x1e/0x20 do_sys_open+0x3a1/0x7d0 __x64_sys_open+0x7e/0xc0 do_syscall_64+0x1b3/0x820 entry_SYSCALL_64_after_hwframe+0x49/0xbe It turned out, gparent = rb_red_parent(parent); tmp = gparent->rb_right; <-- GFP triggered here. Apparently, "gparent" is NULL which indicates "parent" is rbtree's root which is red. Otherwise, it will be treated properly a few lines above. /* * If there is a black parent, we are done. * Otherwise, take some corrective action as, * per 4), we don't want a red root or two * consecutive red nodes. */ if(rb_is_black(parent)) break; Hence, it violates the rule #1 and need a fix up. Reported-by: Esme Signed-off-by: Qian Cai --- lib/rbtree.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/lib/rbtree.c b/lib/rbtree.c index d3ff682fd4b8..acc969ad8de9 100644 --- a/lib/rbtree.c +++ b/lib/rbtree.c @@ -127,6 +127,13 @@ __rb_insert(struct rb_node *node, struct rb_root *root, break; gparent = rb_red_parent(parent); + if (unlikely(!gparent)) { + /* + * The root is red so correct it. + */ + rb_set_parent_color(parent, NULL, RB_BLACK); + break; + } tmp = gparent->rb_right; if (parent != tmp) { /* parent == gparent->rb_left */ -- 2.17.2 (Apple Git-113)