================================================================== BUG: KASAN: use-after-free in skb_frag_size include/linux/skbuff.h:330 [inline] BUG: KASAN: use-after-free in __skb_datagram_iter+0x6b8/0x770 net/core/datagram.c:441 Read of size 4 at addr ffff888033560004 by task syz-fuzzer/8433 CPU: 0 PID: 8433 Comm: syz-fuzzer Not tainted 5.12.0-rc8-next-20210423-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x141/0x1d7 lib/dump_stack.c:120 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:233 __kasan_report mm/kasan/report.c:419 [inline] kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:436 skb_frag_size include/linux/skbuff.h:330 [inline] __skb_datagram_iter+0x6b8/0x770 net/core/datagram.c:441 skb_copy_datagram_iter+0x40/0x50 net/core/datagram.c:533 skb_copy_datagram_msg include/linux/skbuff.h:3602 [inline] tcp_recvmsg_locked+0x1048/0x22f0 net/ipv4/tcp.c:2472 tcp_recvmsg+0x134/0x550 net/ipv4/tcp.c:2550 inet_recvmsg+0x11b/0x5e0 net/ipv4/af_inet.c:852 sock_recvmsg_nosec net/socket.c:888 [inline] sock_recvmsg net/socket.c:906 [inline] sock_recvmsg net/socket.c:902 [inline] sock_read_iter+0x33c/0x470 net/socket.c:979 call_read_iter include/linux/fs.h:2108 [inline] new_sync_read+0x5b7/0x6e0 fs/read_write.c:415 vfs_read+0x35c/0x570 fs/read_write.c:496 ksys_read+0x1ee/0x250 fs/read_write.c:634 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4af19b Code: fb ff eb bd e8 a6 b6 fb ff e9 61 ff ff ff cc e8 9b 82 fb ff 48 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 48 8b 44 24 08 0f 05 <48> 3d 01 f0 ff ff 76 20 48 c7 44 24 28 ff ff ff ff 48 c7 44 24 30 RSP: 002b:000000c0000a3828 EFLAGS: 00000212 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 000000c00001e800 RCX: 00000000004af19b RDX: 0000000000001000 RSI: 000000c000202000 RDI: 0000000000000006 RBP: 000000c0000a3878 R08: 0000000000000001 R09: 0000000000000002 R10: 0000000000007146 R11: 0000000000000212 R12: 0000000000007142 R13: 0000000000000080 R14: 0000000000000004 R15: 0000000000000004 The buggy address belongs to the page: page:ffffea0000cd5800 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x33560 flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000000000 ffffea0000cd6e08 ffffea0000cd5408 0000000000000000 raw: 0000000000000000 0000000000000003 00000000ffffff7f 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88803355ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88803355ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff888033560000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff888033560080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff888033560100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ==================================================================