Re: [syzbot] [can?] [bpf?] KMSAN: uninit-value in bpf_prog_run_generic_xdp

Re: [syzbot] [can?] [bpf?] KMSAN: uninit-value in bpf_prog_run_generic_xdp

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    66a27abac311 Merge tag 'powerpc-6.9-1' of git://git.kernel..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14285ac9180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=48bb382b96e7eda7
dashboard link: https://syzkaller.appspot.com/bug?extid=0e6ddb1ef80986bdfe64
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17ab51c9180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=127d21f1180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/37968fa0451e/disk-66a27aba.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5b288c5c3088/vmlinux-66a27aba.xz
kernel image: https://storage.googleapis.com/syzbot-assets/792ddbf8146d/bzImage-66a27aba.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0e6ddb1ef80986bdfe64@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in bpf_prog_run_generic_xdp+0x13a0/0x1ee0 net/core/dev.c:4876
 bpf_prog_run_generic_xdp+0x13a0/0x1ee0 net/core/dev.c:4876
 netif_receive_generic_xdp net/core/dev.c:4958 [inline]
 do_xdp_generic+0xb68/0x1440 net/core/dev.c:5017
 __netif_receive_skb_core+0x2533/0x6190 net/core/dev.c:5358
 __netif_receive_skb_one_core net/core/dev.c:5536 [inline]
 __netif_receive_skb+0xca/0xa00 net/core/dev.c:5652
 process_backlog+0x480/0x8b0 net/core/dev.c:5981
 __napi_poll+0xe7/0x980 net/core/dev.c:6632
 napi_poll net/core/dev.c:6701 [inline]
 net_rx_action+0x89d/0x1820 net/core/dev.c:6813
 __do_softirq+0x1c0/0x7d7 kernel/softirq.c:554
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu kernel/softirq.c:633 [inline]
 irq_exit_rcu+0x6a/0x130 kernel/softirq.c:645
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
 sysvec_apic_timer_interrupt+0x83/0x90 arch/x86/kernel/apic/apic.c:1043
 asm_sysvec_apic_timer_interrupt+0x1f/0x30 arch/x86/include/asm/idtentry.h:702
 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline]
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x33/0x60 kernel/locking/spinlock.c:194
 unlock_hrtimer_base kernel/time/hrtimer.c:1021 [inline]
 hrtimer_start_range_ns+0x112c/0x11a0 kernel/time/hrtimer.c:1308
 hrtimer_start include/linux/hrtimer.h:275 [inline]
 j1939_tp_schedule_txtimer+0xc2/0x100 net/can/j1939/transport.c:702
 j1939_sk_send_loop net/can/j1939/socket.c:1164 [inline]
 j1939_sk_sendmsg+0x1a0e/0x2730 net/can/j1939/socket.c:1277
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:745
 ____sys_sendmsg+0x877/0xb60 net/socket.c:2584
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
 __sys_sendmsg net/socket.c:2667 [inline]
 __do_sys_sendmsg net/socket.c:2676 [inline]
 __se_sys_sendmsg net/socket.c:2674 [inline]
 __x64_sys_sendmsg+0x307/0x4a0 net/socket.c:2674
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was stored to memory at:
 pskb_expand_head+0x30f/0x19d0 net/core/skbuff.c:2253
 netif_skb_check_for_xdp net/core/dev.c:4921 [inline]
 netif_receive_generic_xdp net/core/dev.c:4952 [inline]
 do_xdp_generic+0x931/0x1440 net/core/dev.c:5017
 __netif_receive_skb_core+0x2533/0x6190 net/core/dev.c:5358
 __netif_receive_skb_one_core net/core/dev.c:5536 [inline]
 __netif_receive_skb+0xca/0xa00 net/core/dev.c:5652
 process_backlog+0x480/0x8b0 net/core/dev.c:5981
 __napi_poll+0xe7/0x980 net/core/dev.c:6632
 napi_poll net/core/dev.c:6701 [inline]
 net_rx_action+0x89d/0x1820 net/core/dev.c:6813
 __do_softirq+0x1c0/0x7d7 kernel/softirq.c:554

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:3804 [inline]
 slab_alloc_node mm/slub.c:3845 [inline]
 kmem_cache_alloc_node+0x613/0xc50 mm/slub.c:3888
 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577
 __alloc_skb+0x35b/0x7a0 net/core/skbuff.c:668
 alloc_skb include/linux/skbuff.h:1318 [inline]
 alloc_skb_with_frags+0xc8/0xbf0 net/core/skbuff.c:6504
 sock_alloc_send_pskb+0xa81/0xbf0 net/core/sock.c:2795
 sock_alloc_send_skb include/net/sock.h:1835 [inline]
 j1939_sk_alloc_skb net/can/j1939/socket.c:878 [inline]
 j1939_sk_send_loop net/can/j1939/socket.c:1142 [inline]
 j1939_sk_sendmsg+0xc0a/0x2730 net/can/j1939/socket.c:1277
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:745
 ____sys_sendmsg+0x877/0xb60 net/socket.c:2584
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
 __sys_sendmsg net/socket.c:2667 [inline]
 __do_sys_sendmsg net/socket.c:2676 [inline]
 __se_sys_sendmsg net/socket.c:2674 [inline]
 __x64_sys_sendmsg+0x307/0x4a0 net/socket.c:2674
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

CPU: 0 PID: 5044 Comm: syz-executor640 Not tainted 6.8.0-syzkaller-11136-g66a27abac311 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
=====================================================


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