[syzbot] memory leak in napi_skb_cache_get

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    64c3dd0b98f5 Merge tag 'xfs-6.1-fixes-4' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1761a066880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7da85296f1024c6a
dashboard link: https://syzkaller.appspot.com/bug?extid=a1fab9d8e5da048ac8a1
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13ac3e61880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17b2040a880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ebc55fa5a058/disk-64c3dd0b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/312317fcea89/vmlinux-64c3dd0b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b5a79a1512f2/bzImage-64c3dd0b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a1fab9d8e5da048ac8a1@xxxxxxxxxxxxxxxxxxxxxxxxx

executing program
executing program
executing program
executing program
executing program
BUG: memory leak
unreferenced object 0xffff88810ef20400 (size 240):
  comm "softirq", pid 0, jiffies 4294950045 (age 43.240s)
  hex dump (first 32 bytes):
    e0 04 1d 0c 81 88 ff ff e0 04 1d 0c 81 88 ff ff  ................
    00 c0 2b 0b 81 88 ff ff 00 00 00 00 00 00 00 00  ..+.............
  backtrace:
    [<ffffffff838525db>] napi_skb_cache_get+0x6b/0x90 net/core/skbuff.c:258
    [<ffffffff83852615>] __napi_build_skb+0x15/0x50 net/core/skbuff.c:387
    [<ffffffff838529e9>] __napi_alloc_skb+0x129/0x260 net/core/skbuff.c:691
    [<ffffffff82a1e9df>] napi_alloc_skb include/linux/skbuff.h:3212 [inline]
    [<ffffffff82a1e9df>] page_to_skb+0x11f/0x770 drivers/net/virtio_net.c:499
    [<ffffffff82a21dee>] receive_mergeable drivers/net/virtio_net.c:1122 [inline]
    [<ffffffff82a21dee>] receive_buf+0x6ae/0x2d70 drivers/net/virtio_net.c:1261
    [<ffffffff82a246fe>] virtnet_receive drivers/net/virtio_net.c:1556 [inline]
    [<ffffffff82a246fe>] virtnet_poll+0x24e/0x6f0 drivers/net/virtio_net.c:1674
    [<ffffffff8388909d>] __napi_poll+0x3d/0x290 net/core/dev.c:6498
    [<ffffffff838898cc>] napi_poll net/core/dev.c:6565 [inline]
    [<ffffffff838898cc>] net_rx_action+0x3ac/0x490 net/core/dev.c:6676
    [<ffffffff84a000eb>] __do_softirq+0xeb/0x2ef kernel/softirq.c:571
    [<ffffffff8124c9b6>] invoke_softirq kernel/softirq.c:445 [inline]
    [<ffffffff8124c9b6>] __irq_exit_rcu+0xc6/0x110 kernel/softirq.c:650
    [<ffffffff84609b08>] common_interrupt+0xb8/0xd0 arch/x86/kernel/irq.c:240
    [<ffffffff84800c22>] asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:640
    [<ffffffff84622dc9>] native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
    [<ffffffff84622dc9>] arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
    [<ffffffff84622dc9>] acpi_safe_halt drivers/acpi/processor_idle.c:112 [inline]
    [<ffffffff84622dc9>] acpi_idle_do_entry+0xc9/0xe0 drivers/acpi/processor_idle.c:572
    [<ffffffff846232e0>] acpi_idle_enter+0x150/0x230 drivers/acpi/processor_idle.c:709
    [<ffffffff83432934>] cpuidle_enter_state+0xc4/0x740 drivers/cpuidle/cpuidle.c:239
    [<ffffffff83433009>] cpuidle_enter+0x29/0x40 drivers/cpuidle/cpuidle.c:356



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