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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 ffff88802a398004 by task syz-fuzzer/8439

CPU: 0 PID: 8439 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:000000c0000a1828 EFLAGS: 00000212 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 000000c00001c000 RCX: 00000000004af19b
RDX: 0000000000001000 RSI: 000000c000202000 RDI: 0000000000000006
RBP: 000000c0000a1878 R08: 0000000000000001 R09: 0000000000000002
R10: 00000000000057d4 R11: 0000000000000212 R12: 00000000000057d0
R13: 0000000000000200 R14: 0000000000000020 R15: 0000000000000010

Allocated by task 1:
 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_kmalloc mm/kasan/common.c:507 [inline]
 ____kasan_kmalloc mm/kasan/common.c:466 [inline]
 __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:516
 kmalloc include/linux/slab.h:563 [inline]
 tomoyo_realpath_from_path+0xc3/0x620 security/tomoyo/realpath.c:254
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x21b/0x400 security/tomoyo/file.c:822
 security_inode_getattr+0xcf/0x140 security/security.c:1332
 vfs_getattr fs/stat.c:139 [inline]
 vfs_statx+0x164/0x390 fs/stat.c:207
 vfs_fstatat fs/stat.c:225 [inline]
 vfs_lstat include/linux/fs.h:3384 [inline]
 __do_sys_newlstat+0x91/0x110 fs/stat.c:380
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 4174:
 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]
 kfree+0xe5/0x7f0 mm/slub.c:4245
 tomoyo_realpath_from_path+0x191/0x620 security/tomoyo/realpath.c:291
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x21b/0x400 security/tomoyo/file.c:822
 security_inode_getattr+0xcf/0x140 security/security.c:1332
 vfs_getattr fs/stat.c:139 [inline]
 vfs_statx+0x164/0x390 fs/stat.c:207
 vfs_fstatat fs/stat.c:225 [inline]
 vfs_lstat include/linux/fs.h:3384 [inline]
 __do_sys_newlstat+0x91/0x110 fs/stat.c:380
 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 ffff88802a398000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 4 bytes inside of
 4096-byte region [ffff88802a398000, ffff88802a399000)
The buggy address belongs to the page:
page:ffffea0000a8e600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2a398
head:ffffea0000a8e600 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 0000000100000001 ffff888011042140
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88802a397f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88802a397f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88802a398000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88802a398080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802a398100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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