7324157b8a
A recent change to fix up DSA device behavior made the assumption that all skbs passing through the flow disector will be associated with a device. This does not appear to be a safe assumption. Syzkaller found the crash below by attaching a BPF socket filter that tries to find the payload offset of a packet passing between two unix sockets. kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 0 PID: 2940 Comm: syzkaller872007 Not tainted 4.13.0-rc4-next-20170811 #1 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801d1b425c0 task.stack: ffff8801d0bc0000 RIP: 0010:__skb_flow_dissect+0xdcd/0x3ae0 net/core/flow_dissector.c:445 RSP: 0018:ffff8801d0bc7340 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000060 RSI: ffffffff856dc080 RDI: 0000000000000300 RBP: ffff8801d0bc7870 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000008 R11: ffffed003a178f1e R12: 0000000000000000 R13: 0000000000000000 R14: ffffffff856dc080 R15: ffff8801ce223140 FS: 00000000016ed880(0000) GS:ffff8801dc000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020008000 CR3: 00000001ce22d000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: skb_flow_dissect_flow_keys include/linux/skbuff.h:1176 [inline] skb_get_poff+0x9a/0x1a0 net/core/flow_dissector.c:1079 ______skb_get_pay_offset net/core/filter.c:114 [inline] __skb_get_pay_offset+0x15/0x20 net/core/filter.c:112 Code: 80 3c 02 00 44 89 6d 10 0f 85 44 2b 00 00 4d 8b 67 20 48 b8 00 00 00 00 00 fc ff df 49 8d bc 24 00 03 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 13 2b 00 00 4d 8b a4 24 00 03 00 00 4d 85 e4 RIP: __skb_flow_dissect+0xdcd/0x3ae0 net/core/flow_dissector.c:445 RSP: ffff8801d0bc7340 Fixes: 43e665287f93 ("net-next: dsa: fix flow dissection") Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Craig Gallek <kraig@google.com> Reviewed-by: Andrew Lunn <andrew@lunn.ch> 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.