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syzbot/kasan detected a double free in sctp_sendmsg_to_asoc: BUG: KASAN: use-after-free in sctp_association_free+0x7b7/0x930 net/sctp/associola.c:332 Read of size 8 at addr ffff8801d8006ae0 by task syzkaller914861/4202 CPU: 1 PID: 4202 Comm: syzkaller914861 Not tainted 4.16.0-rc4+ #258 Hardware name: Google Google Compute Engine/Google Compute Engine 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report+0x23c/0x360 mm/kasan/report.c:412 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 sctp_association_free+0x7b7/0x930 net/sctp/associola.c:332 sctp_sendmsg+0xc67/0x1a80 net/sctp/socket.c:2075 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763 sock_sendmsg_nosec net/socket.c:629 [inline] sock_sendmsg+0xca/0x110 net/socket.c:639 SYSC_sendto+0x361/0x5c0 net/socket.c:1748 SyS_sendto+0x40/0x50 net/socket.c:1716 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 This was introduced by commit: f84af33 sctp: factor out sctp_sendmsg_to_asoc from sctp_sendmsg As the newly refactored function moved the wait_for_sndbuf call to a point after the association was connected, allowing for peeloff events to occur, which in turn caused wait_for_sndbuf to return -EPIPE which was not caught by the logic that determines if an association should be freed or not. Fix it the easy way by returning the ordering of sctp_primitive_ASSOCIATE and sctp_wait_for_sndbuf to the old order, to ensure that EPIPE will not happen. Tested by myself using the syzbot reproducers with positive results Signed-off-by: Neil Horman <nhorman@tuxdriver.com> CC: davem@davemloft.net CC: Xin Long <lucien.xin@gmail.com> Reported-by: syzbot+a4e4112c3aff00c8cfd8@syzkaller.appspotmail.com Reviewed-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.