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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 ffff888032aa0004 by task syz-fuzzer/8443

CPU: 0 PID: 8443 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:000000c00016f840 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 000000c00001e800 RCX: 00000000004af19b
RDX: 0000000000001000 RSI: 000000c0001a8000 RDI: 0000000000000006
RBP: 000000c00016f890 R08: 0000000000000001 R09: 0000000000000002
R10: 000000000000338e R11: 0000000000000202 R12: ffffffffffffffff
R13: 0000000000001000 R14: 0000000000000020 R15: 0000000000000020

The buggy address belongs to the page:
page:ffffea0000caa800 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x32aa0
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000779608 ffffea0000b10c08 0000000000000000
raw: 0000000000000000 0000000000000003 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888032a9ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888032a9ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888032aa0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888032aa0080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888032aa0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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