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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id n71sm21946926qkl.72.2019.01.11.08.52.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 11 Jan 2019 08:52:11 -0800 (PST) From: Qian Cai 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 Subject: [PATCH] rbtree: fix the red root Date: Fri, 11 Jan 2019 11:51:45 -0500 Message-Id: <20190111165145.23628-1-cai@lca.pw> X-Mailer: git-send-email 2.17.2 (Apple Git-113) In-Reply-To: References: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP 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 Reviewed-by: Joey Pabalinas Tested-by: Joey Pabalinas --- 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 */