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BUG: KASAN: use-after-free in p9_client_clunk+0x1fc/0x240 net/9p/client.c:1503
Read of size 8 at addr ffff8880a20cef00 by task syz-executor.0/3267

CPU: 1 PID: 3267 Comm: syz-executor.0 Not tainted 4.14.300-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
9pnet: Insufficient options for proto=fd
 kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
 p9_client_clunk+0x1fc/0x240 net/9p/client.c:1503
 v9fs_mount+0x69f/0x860 fs/9p/vfs_super.c:200
 mount_fs+0x92/0x2a0 fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 fs/namespace.c:1046
 vfs_kern_mount fs/namespace.c:1036 [inline]
 do_new_mount fs/namespace.c:2572 [inline]
 do_mount+0xe65/0x2a30 fs/namespace.c:2905
 SYSC_mount fs/namespace.c:3121 [inline]
 SyS_mount+0xa8/0x120 fs/namespace.c:3098
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x5e/0xd3

Allocated by task 3267:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x131/0x3d0 mm/slab.c:3618
9pnet: Insufficient options for proto=fd
 kmalloc include/linux/slab.h:488 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 p9_fid_create+0x47/0x360 net/9p/client.c:918
 p9_client_attach+0x6d/0x750 net/9p/client.c:1156
 v9fs_session_init+0xc03/0x1540 fs/9p/v9fs.c:471
 v9fs_mount+0x73/0x860 fs/9p/vfs_super.c:135
 mount_fs+0x92/0x2a0 fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 fs/namespace.c:1046
 vfs_kern_mount fs/namespace.c:1036 [inline]
 do_new_mount fs/namespace.c:2572 [inline]
 do_mount+0xe65/0x2a30 fs/namespace.c:2905
 SYSC_mount fs/namespace.c:3121 [inline]
 SyS_mount+0xa8/0x120 fs/namespace.c:3098
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x5e/0xd3

Freed by task 3267:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xc9/0x250 mm/slab.c:3815
 p9_client_destroy.cold+0x67/0xaa net/9p/client.c:1119
 v9fs_session_close+0x45/0x2c0 fs/9p/v9fs.c:511
 v9fs_kill_super+0x49/0x90 fs/9p/vfs_super.c:233
 deactivate_locked_super+0x6c/0xd0 fs/super.c:319
 sget_userns+0x9c4/0xc10 fs/super.c:537
 sget+0xd1/0x110 fs/super.c:572
 v9fs_mount+0x9e/0x860 fs/9p/vfs_super.c:141
 mount_fs+0x92/0x2a0 fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 fs/namespace.c:1046
 vfs_kern_mount fs/namespace.c:1036 [inline]
 do_new_mount fs/namespace.c:2572 [inline]
 do_mount+0xe65/0x2a30 fs/namespace.c:2905
 SYSC_mount fs/namespace.c:3121 [inline]
 SyS_mount+0xa8/0x120 fs/namespace.c:3098
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x5e/0xd3

The buggy address belongs to the object at ffff8880a20cef00
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 0 bytes inside of
 96-byte region [ffff8880a20cef00, ffff8880a20cef60)
The buggy address belongs to the page:
page:ffffea0002883380 count:1 mapcount:0 mapping:ffff8880a20ce000 index:0xffff8880a20ce600
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffff8880a20ce000 ffff8880a20ce600 0000000100000017
raw: ffffea0002577d20 ffffea00028e15a0 ffff88813fe744c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a20cee00: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff8880a20cee80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff8880a20cef00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                   ^
 ffff8880a20cef80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff8880a20cf000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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