bbbe211c29
do_xdp_generic must be called inside rcu critical section with preempt disabled to ensure BPF programs are valid and per-cpu variables used for redirect operations are consistent. This patch ensures this is true and fixes the splat below. The netif_receive_skb_internal() code path is now broken into two rcu critical sections. I decided it was better to limit the preempt_enable/disable block to just the xdp static key portion and the fallout is more rcu_read_lock/unlock calls. Seems like the best option to me. [ 607.596901] ============================= [ 607.596906] WARNING: suspicious RCU usage [ 607.596912] 4.13.0-rc4+ #570 Not tainted [ 607.596917] ----------------------------- [ 607.596923] net/core/dev.c:3948 suspicious rcu_dereference_check() usage! [ 607.596927] [ 607.596927] other info that might help us debug this: [ 607.596927] [ 607.596933] [ 607.596933] rcu_scheduler_active = 2, debug_locks = 1 [ 607.596938] 2 locks held by pool/14624: [ 607.596943] #0: (rcu_read_lock_bh){......}, at: [<ffffffff95445ffd>] ip_finish_output2+0x14d/0x890 [ 607.596973] #1: (rcu_read_lock_bh){......}, at: [<ffffffff953c8e3a>] __dev_queue_xmit+0x14a/0xfd0 [ 607.597000] [ 607.597000] stack backtrace: [ 607.597006] CPU: 5 PID: 14624 Comm: pool Not tainted 4.13.0-rc4+ #570 [ 607.597011] Hardware name: Dell Inc. Precision Tower 5810/0HHV7N, BIOS A17 03/01/2017 [ 607.597016] Call Trace: [ 607.597027] dump_stack+0x67/0x92 [ 607.597040] lockdep_rcu_suspicious+0xdd/0x110 [ 607.597054] do_xdp_generic+0x313/0xa50 [ 607.597068] ? time_hardirqs_on+0x5b/0x150 [ 607.597076] ? mark_held_locks+0x6b/0xc0 [ 607.597088] ? netdev_pick_tx+0x150/0x150 [ 607.597117] netif_rx_internal+0x205/0x3f0 [ 607.597127] ? do_xdp_generic+0xa50/0xa50 [ 607.597144] ? lock_downgrade+0x2b0/0x2b0 [ 607.597158] ? __lock_is_held+0x93/0x100 [ 607.597187] netif_rx+0x119/0x190 [ 607.597202] loopback_xmit+0xfd/0x1b0 [ 607.597214] dev_hard_start_xmit+0x127/0x4e0 Fixes: d445516966dc ("net: xdp: support xdp generic on virtual devices") Fixes: b5cdae3291f7 ("net: Generic XDP") Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> 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.