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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 ffff888014c10004 by task syz-fuzzer/8464

CPU: 0 PID: 8464 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:000000c000367828 EFLAGS: 00000212 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 000000c00001c000 RCX: 00000000004af19b
RDX: 0000000000001000 RSI: 000000c0001e9000 RDI: 0000000000000006
RBP: 000000c000367878 R08: 0000000000000001 R09: 0000000000000002
R10: 000000000000672c R11: 0000000000000212 R12: 0000000000006726
R13: 0000000000001000 R14: 0000000000000040 R15: 0000000000000008

Allocated by task 8413:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:428 [inline]
 __kasan_slab_alloc+0x84/0xa0 mm/kasan/common.c:461
 kasan_slab_alloc include/linux/kasan.h:236 [inline]
 slab_post_alloc_hook mm/slab.h:527 [inline]
 slab_alloc_node mm/slub.c:2924 [inline]
 slab_alloc mm/slub.c:2932 [inline]
 kmem_cache_alloc+0x219/0x3a0 mm/slub.c:2937
 getname_flags.part.0+0x50/0x4f0 fs/namei.c:138
 getname_flags fs/namei.c:2734 [inline]
 user_path_at_empty+0xa1/0x100 fs/namei.c:2734
 do_readlinkat+0xcd/0x2f0 fs/stat.c:425
 __do_sys_readlinkat fs/stat.c:452 [inline]
 __se_sys_readlinkat fs/stat.c:449 [inline]
 __x64_sys_readlinkat+0x93/0xf0 fs/stat.c:449
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 20558:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
 ____kasan_slab_free mm/kasan/common.c:360 [inline]
 ____kasan_slab_free mm/kasan/common.c:325 [inline]
 __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:368
 kasan_slab_free include/linux/kasan.h:212 [inline]
 slab_free_hook mm/slub.c:1593 [inline]
 slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1618
 slab_free mm/slub.c:3178 [inline]
 kmem_cache_free+0x97/0x750 mm/slub.c:3194
 putname+0xe1/0x120 fs/namei.c:259
 filename_lookup+0x3c3/0x570 fs/namei.c:2464
 do_readlinkat+0xcd/0x2f0 fs/stat.c:425
 __do_sys_readlinkat fs/stat.c:452 [inline]
 __se_sys_readlinkat fs/stat.c:449 [inline]
 __x64_sys_readlinkat+0x93/0xf0 fs/stat.c:449
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff888014c10000
 which belongs to the cache names_cache of size 4096
The buggy address is located 4 bytes inside of
 4096-byte region [ffff888014c10000, ffff888014c11000)
The buggy address belongs to the page:
page:ffffea0000530400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14c10
head:ffffea0000530400 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff8880111be280
raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888014c0ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888014c0ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888014c10000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888014c10080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888014c10100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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