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BUG: KASAN: use-after-free in io_uring_show_cred+0x5bb/0x5f0 fs/io_uring.c:9219
Read of size 8 at addr ffff8880292f4c20 by task syz-executor.5/17505

CPU: 1 PID: 17505 Comm: syz-executor.5 Not tainted 5.10.0-rc2-next-20201104-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x4c8 mm/kasan/report.c:385
 __kasan_report mm/kasan/report.c:545 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
 io_uring_show_cred+0x5bb/0x5f0 fs/io_uring.c:9219
 idr_for_each+0x113/0x220 lib/idr.c:208
 __io_uring_show_fdinfo fs/io_uring.c:9272 [inline]
 io_uring_show_fdinfo+0x923/0xda0 fs/io_uring.c:9294
 seq_show+0x4a8/0x700 fs/proc/fd.c:65
 seq_read+0x432/0x1070 fs/seq_file.c:208
 do_loop_readv_writev fs/read_write.c:761 [inline]
 do_loop_readv_writev fs/read_write.c:748 [inline]
 do_iter_read+0x48e/0x6e0 fs/read_write.c:803
 vfs_readv+0xe5/0x150 fs/read_write.c:921
 do_preadv fs/read_write.c:1013 [inline]
 __do_sys_preadv fs/read_write.c:1063 [inline]
 __se_sys_preadv fs/read_write.c:1058 [inline]
 __x64_sys_preadv+0x231/0x310 fs/read_write.c:1058
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45deb9
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6c3b7ccc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000025e40 RCX: 000000000045deb9
RDX: 0000000000000333 RSI: 00000000200017c0 RDI: 0000000000000005
RBP: 000000000118bf70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffe330c7a7f R14: 00007f6c3b7cd9c0 R15: 000000000118bf2c

Allocated by task 17511:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:461
 kmalloc include/linux/slab.h:557 [inline]
 kzalloc include/linux/slab.h:664 [inline]
 tomoyo_encode2.part.0+0xe9/0x3a0 security/tomoyo/realpath.c:45
 tomoyo_encode2 security/tomoyo/realpath.c:31 [inline]
 tomoyo_encode+0x28/0x50 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x186/0x620 security/tomoyo/realpath.c:288
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x21b/0x400 security/tomoyo/file.c:822
 tomoyo_path_symlink+0x94/0xe0 security/tomoyo/tomoyo.c:200
 security_path_symlink+0xdf/0x150 security/security.c:1110
 do_symlinkat+0x123/0x2c0 fs/namei.c:3985
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 17511:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0x102/0x140 mm/kasan/common.c:422
 slab_free_hook mm/slub.c:1544 [inline]
 slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1577
 slab_free mm/slub.c:3140 [inline]
 kfree+0xdb/0x360 mm/slub.c:4122
 tomoyo_path_perm+0x23d/0x400 security/tomoyo/file.c:842
 tomoyo_path_symlink+0x94/0xe0 security/tomoyo/tomoyo.c:200
 security_path_symlink+0xdf/0x150 security/security.c:1110
 do_symlinkat+0x123/0x2c0 fs/namei.c:3985
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8880292f4c00
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 32 bytes inside of
 96-byte region [ffff8880292f4c00, ffff8880292f4c60)
The buggy address belongs to the page:
page:00000000438ffd75 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x292f4
flags: 0xfff00000000200(slab)
raw: 00fff00000000200 ffffea00004a8880 0000001900000019 ffff888010041780
raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880292f4b00: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff8880292f4b80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>ffff8880292f4c00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                               ^
 ffff8880292f4c80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
 ffff8880292f4d00: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
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