-
Notifications
You must be signed in to change notification settings - Fork 143
xdp: fix page_pool leaks #10022
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
base: bpf_base
Are you sure you want to change the base?
xdp: fix page_pool leaks #10022
Conversation
Upstream branch: f6fddc6 |
Upstream branch: f6fddc6 |
371d3e0
to
98873e8
Compare
a36ad11
to
b1f9967
Compare
Upstream branch: a1e83d4 |
98873e8
to
a2a8bd3
Compare
b1f9967
to
9761e9e
Compare
Upstream branch: a1e83d4 |
a2a8bd3
to
7fd3cc0
Compare
9761e9e
to
2cf3f91
Compare
Currently, generic XDP hook uses xdp_rxq_info from netstack Rx queues which do not have its XDP memory model registered. There is a case when XDP program calls bpf_xdp_adjust_tail() BPF helper, which in turn releases underlying memory. This happens when it consumes enough amount of bytes and when XDP buffer has fragments. For this action the memory model knowledge passed to XDP program is crucial so that core can call suitable function for freeing/recycling the page. For netstack queues it defaults to MEM_TYPE_PAGE_SHARED (0) due to lack of mem model registration. The problem we're fixing here is when kernel copied the skb to new buffer backed by system's page_pool and XDP buffer is built around it. Then when bpf_xdp_adjust_tail() calls __xdp_return(), it acts incorrectly due to mem type not being set to MEM_TYPE_PAGE_POOL and causes a page leak. Pull out the existing code from bpf_prog_run_generic_xdp() that init/prepares xdp_buff onto new helper xdp_convert_skb_to_buff() and embed there rxq's mem_type initialization that is assigned to xdp_buff. This problem was triggered by syzbot as well as AF_XDP test suite which is about to be integrated to BPF CI. Reported-by: [email protected] Closes: https://lore.kernel.org/netdev/[email protected]/ Fixes: e6d5dbd ("xdp: add multi-buff support for xdp running in generic mode") Tested-by: Ihor Solodrai <[email protected]> Co-developed-by: Octavian Purdila <[email protected]> Signed-off-by: Octavian Purdila <[email protected]> # whole analysis, testing, initiating a fix Signed-off-by: Maciej Fijalkowski <[email protected]> # commit msg and proposed more robust fix Reviewed-by: Toke Høiland-Jørgensen <[email protected]>
Veth calls skb_pp_cow_data() which makes the underlying memory to originate from system page_pool. For CONFIG_DEBUG_VM=y and XDP program that uses bpf_xdp_adjust_tail(), following splat was observed: [ 32.204881] BUG: Bad page state in process test_progs pfn:11c98b [ 32.207167] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11c98b [ 32.210084] flags: 0x1fffe0000000000(node=0|zone=1|lastcpupid=0x7fff) [ 32.212493] raw: 01fffe0000000000 dead000000000040 ff11000123c9b000 0000000000000000 [ 32.218056] raw: 0000000000000000 0000000000000001 00000000ffffffff 0000000000000000 [ 32.220900] page dumped because: page_pool leak [ 32.222636] Modules linked in: bpf_testmod(O) bpf_preload [ 32.224632] CPU: 6 UID: 0 PID: 3612 Comm: test_progs Tainted: G O 6.17.0-rc5-gfec474d29325 #6969 PREEMPT [ 32.224638] Tainted: [O]=OOT_MODULE [ 32.224639] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [ 32.224641] Call Trace: [ 32.224644] <IRQ> [ 32.224646] dump_stack_lvl+0x4b/0x70 [ 32.224653] bad_page.cold+0xbd/0xe0 [ 32.224657] __free_frozen_pages+0x838/0x10b0 [ 32.224660] ? skb_pp_cow_data+0x782/0xc30 [ 32.224665] bpf_xdp_shrink_data+0x221/0x530 [ 32.224668] ? skb_pp_cow_data+0x6d1/0xc30 [ 32.224671] bpf_xdp_adjust_tail+0x598/0x810 [ 32.224673] ? xsk_destruct_skb+0x321/0x800 [ 32.224678] bpf_prog_004ac6bb21de57a7_xsk_xdp_adjust_tail+0x52/0xd6 [ 32.224681] veth_xdp_rcv_skb+0x45d/0x15a0 [ 32.224684] ? get_stack_info_noinstr+0x16/0xe0 [ 32.224688] ? veth_set_channels+0x920/0x920 [ 32.224691] ? get_stack_info+0x2f/0x80 [ 32.224693] ? unwind_next_frame+0x3af/0x1df0 [ 32.224697] veth_xdp_rcv.constprop.0+0x38a/0xbe0 [ 32.224700] ? common_startup_64+0x13e/0x148 [ 32.224703] ? veth_xdp_rcv_one+0xcd0/0xcd0 [ 32.224706] ? stack_trace_save+0x84/0xa0 [ 32.224709] ? stack_depot_save_flags+0x28/0x820 [ 32.224713] ? __resched_curr.constprop.0+0x332/0x3b0 [ 32.224716] ? timerqueue_add+0x217/0x320 [ 32.224719] veth_poll+0x115/0x5e0 [ 32.224722] ? veth_xdp_rcv.constprop.0+0xbe0/0xbe0 [ 32.224726] ? update_load_avg+0x1cb/0x12d0 [ 32.224730] ? update_cfs_group+0x121/0x2c0 [ 32.224733] __napi_poll+0xa0/0x420 [ 32.224736] net_rx_action+0x901/0xe90 [ 32.224740] ? run_backlog_napi+0x50/0x50 [ 32.224743] ? clockevents_program_event+0x1cc/0x280 [ 32.224746] ? hrtimer_interrupt+0x31e/0x7c0 [ 32.224749] handle_softirqs+0x151/0x430 [ 32.224752] do_softirq+0x3f/0x60 [ 32.224755] </IRQ> It's because xdp_rxq with mem model set to MEM_TYPE_PAGE_SHARED was used when initializing xdp_buff. Fix this by using new helper xdp_convert_skb_to_buff() that, besides init/prepare xdp_buff, will check if page used for linear part of xdp_buff comes from page_pool. We assume that linear data and frags will have same memory provider as currently XDP API does not provide us a way to distinguish it (the mem model is registered for *whole* Rx queue and here we speak about single buffer granularity). In order to meet expected skb layout by new helper, pull the mac header before conversion from skb to xdp_buff. However, that is not enough as before releasing xdp_buff out of veth via XDP_{TX,REDIRECT}, mem type on xdp_rxq associated with xdp_buff is restored to its original model. We need to respect previous setting at least until buff is converted to frame, as frame carries the mem_type. Add a page_pool variant of veth_xdp_get() so that we avoid refcount underflow when draining page frag. Fixes: 0ebab78 ("net: veth: add page_pool for page recycling") Reported-by: Alexei Starovoitov <[email protected]> Closes: https://lore.kernel.org/bpf/CAADnVQ+bBofJDfieyOYzSmSujSfJwDTQhiz3aJw7hE+4E2_iPA@mail.gmail.com/ Signed-off-by: Maciej Fijalkowski <[email protected]>
Upstream branch: 1c64efc |
7fd3cc0
to
09d7b76
Compare
Pull request for series with
subject: xdp: fix page_pool leaks
version: 2
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1012904