CVE-2022-49856

In the Linux kernel, the following vulnerability has been resolved: net: tun: call napi_schedule_prep() to ensure we own a napi A recent patch exposed another issue in napi_get_frags() caught by syzbot [1] Before feeding packets to GRO, and calling napi_complete() we must first grab NAPI_STATE_SCHED. [1] WARNING: CPU: 0 PID: 3612 at net/core/dev.c:6076 napi_complete_done+0x45b/0x880 net/core/dev.c:6076 Modules linked in: CPU: 0 PID: 3612 Comm: syz-executor408 Not tainted 6.1.0-rc3-syzkaller-00175-g1118b2049d77 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 RIP: 0010:napi_complete_done+0x45b/0x880 net/core/dev.c:6076 Code: c1 ea 03 0f b6 14 02 4c 89 f0 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 24 04 00 00 41 89 5d 1c e9 73 fc ff ff e8 b5 53 22 fa <0f> 0b e9 82 fe ff ff e8 a9 53 22 fa 48 8b 5c 24 08 31 ff 48 89 de RSP: 0018:ffffc90003c4f920 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000030 RCX: 0000000000000000 RDX: ffff8880251c0000 RSI: ffffffff875a58db RDI: 0000000000000007 RBP: 0000000000000001 R08: 0000000000000007 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: ffff888072d02628 R13: ffff888072d02618 R14: ffff888072d02634 R15: 0000000000000000 FS: 0000555555f13300(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055c44d3892b8 CR3: 00000000172d2000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> napi_complete include/linux/netdevice.h:510 [inline] tun_get_user+0x206d/0x3a60 drivers/net/tun.c:1980 tun_chr_write_iter+0xdb/0x200 drivers/net/tun.c:2027 call_write_iter include/linux/fs.h:2191 [inline] do_iter_readv_writev+0x20b/0x3b0 fs/read_write.c:735 do_iter_write+0x182/0x700 fs/read_write.c:861 vfs_writev+0x1aa/0x630 fs/read_write.c:934 do_writev+0x133/0x2f0 fs/read_write.c:977 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f37021a3c19