From: Eric Dumazet edumazet@google.com
commit 8a9896177784063d01068293caea3f74f6830ff6 upstream.
Another syzbot report [1] is about tp->status lockless reads from __packet_get_status()
[1] BUG: KCSAN: data-race in __packet_rcv_has_room / __packet_set_status
write to 0xffff888117d7c080 of 8 bytes by interrupt on cpu 0: __packet_set_status+0x78/0xa0 net/packet/af_packet.c:407 tpacket_rcv+0x18bb/0x1a60 net/packet/af_packet.c:2483 deliver_skb net/core/dev.c:2173 [inline] __netif_receive_skb_core+0x408/0x1e80 net/core/dev.c:5337 __netif_receive_skb_one_core net/core/dev.c:5491 [inline] __netif_receive_skb+0x57/0x1b0 net/core/dev.c:5607 process_backlog+0x21f/0x380 net/core/dev.c:5935 __napi_poll+0x60/0x3b0 net/core/dev.c:6498 napi_poll net/core/dev.c:6565 [inline] net_rx_action+0x32b/0x750 net/core/dev.c:6698 __do_softirq+0xc1/0x265 kernel/softirq.c:571 invoke_softirq kernel/softirq.c:445 [inline] __irq_exit_rcu+0x57/0xa0 kernel/softirq.c:650 sysvec_apic_timer_interrupt+0x6d/0x80 arch/x86/kernel/apic/apic.c:1106 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645 smpboot_thread_fn+0x33c/0x4a0 kernel/smpboot.c:112 kthread+0x1d7/0x210 kernel/kthread.c:379 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
read to 0xffff888117d7c080 of 8 bytes by interrupt on cpu 1: __packet_get_status net/packet/af_packet.c:436 [inline] packet_lookup_frame net/packet/af_packet.c:524 [inline] __tpacket_has_room net/packet/af_packet.c:1255 [inline] __packet_rcv_has_room+0x3f9/0x450 net/packet/af_packet.c:1298 tpacket_rcv+0x275/0x1a60 net/packet/af_packet.c:2285 deliver_skb net/core/dev.c:2173 [inline] dev_queue_xmit_nit+0x38a/0x5e0 net/core/dev.c:2243 xmit_one net/core/dev.c:3574 [inline] dev_hard_start_xmit+0xcf/0x3f0 net/core/dev.c:3594 __dev_queue_xmit+0xefb/0x1d10 net/core/dev.c:4244 dev_queue_xmit include/linux/netdevice.h:3088 [inline] can_send+0x4eb/0x5d0 net/can/af_can.c:276 bcm_can_tx+0x314/0x410 net/can/bcm.c:302 bcm_tx_timeout_handler+0xdb/0x260 __run_hrtimer kernel/time/hrtimer.c:1685 [inline] __hrtimer_run_queues+0x217/0x700 kernel/time/hrtimer.c:1749 hrtimer_run_softirq+0xd6/0x120 kernel/time/hrtimer.c:1766 __do_softirq+0xc1/0x265 kernel/softirq.c:571 run_ksoftirqd+0x17/0x20 kernel/softirq.c:939 smpboot_thread_fn+0x30a/0x4a0 kernel/smpboot.c:164 kthread+0x1d7/0x210 kernel/kthread.c:379 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
value changed: 0x0000000000000000 -> 0x0000000020000081
Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 6.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Fixes: 69e3c75f4d54 ("net: TX_RING and packet mmap") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Eric Dumazet edumazet@google.com Reviewed-by: Willem de Bruijn willemb@google.com Link: https://lore.kernel.org/r/20230803145600.2937518-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/packet/af_packet.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)
--- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -363,18 +363,20 @@ static void __packet_set_status(struct p { union tpacket_uhdr h;
+ /* WRITE_ONCE() are paired with READ_ONCE() in __packet_get_status */ + h.raw = frame; switch (po->tp_version) { case TPACKET_V1: - h.h1->tp_status = status; + WRITE_ONCE(h.h1->tp_status, status); flush_dcache_page(pgv_to_page(&h.h1->tp_status)); break; case TPACKET_V2: - h.h2->tp_status = status; + WRITE_ONCE(h.h2->tp_status, status); flush_dcache_page(pgv_to_page(&h.h2->tp_status)); break; case TPACKET_V3: - h.h3->tp_status = status; + WRITE_ONCE(h.h3->tp_status, status); flush_dcache_page(pgv_to_page(&h.h3->tp_status)); break; default: @@ -391,17 +393,19 @@ static int __packet_get_status(const str
smp_rmb();
+ /* READ_ONCE() are paired with WRITE_ONCE() in __packet_set_status */ + h.raw = frame; switch (po->tp_version) { case TPACKET_V1: flush_dcache_page(pgv_to_page(&h.h1->tp_status)); - return h.h1->tp_status; + return READ_ONCE(h.h1->tp_status); case TPACKET_V2: flush_dcache_page(pgv_to_page(&h.h2->tp_status)); - return h.h2->tp_status; + return READ_ONCE(h.h2->tp_status); case TPACKET_V3: flush_dcache_page(pgv_to_page(&h.h3->tp_status)); - return h.h3->tp_status; + return READ_ONCE(h.h3->tp_status); default: WARN(1, "TPACKET version not supported.\n"); BUG();