From b2e1f10f138c6cc03a2f5c940b6c4963b07c7296 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Thu, 14 Sep 2017 17:14:41 -0400 Subject: [PATCH] packet: hold bind lock when rebinding to fanout hook commit 008ba2a13f2d04c947adc536d19debb8fe66f110 upstream. Packet socket bind operations must hold the po->bind_lock. This keeps po->running consistent with whether the socket is actually on a ptype list to receive packets. fanout_add unbinds a socket and its packet_rcv/tpacket_rcv call, then binds the fanout object to receive through packet_rcv_fanout. Make it hold the po->bind_lock when testing po->running and rebinding. Else, it can race with other rebind operations, such as that in packet_set_ring from packet_rcv to tpacket_rcv. Concurrent updates can result in a socket being added to a fanout group twice, causing use-after-free KASAN bug reports, among others. Reported independently by both trinity and syzkaller. Verified that the syzkaller reproducer passes after this patch. Fixes: dc99f600698d ("packet: Add fanout support.") Reported-by: nixioaming Signed-off-by: Willem de Bruijn Signed-off-by: David S. Miller [bwh: Backported to 3.2: use atomic_read() not refcount_read()] Signed-off-by: Ben Hutchings --- Reading git-format-patch failed