memory leak in fasync_helper

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    bf929479 Merge branch 'for-linus' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123e91e2e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=874c75a332209d41
dashboard link: https://syzkaller.appspot.com/bug?extid=4b1fe8105f8044a26162
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=120faee2e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=178a0ef6e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4b1fe8105f8044a26162@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: memory leak
unreferenced object 0xffff88812a4082a0 (size 48):
  comm "syz-executor670", pid 6989, jiffies 4294952355 (age 19.520s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 01 46 00 00 03 00 00 00  .........F......
    00 00 00 00 00 00 00 00 00 6b 05 1f 81 88 ff ff  .........k......
  backtrace:
    [<000000002a74b343>] kmemleak_alloc_recursive  
include/linux/kmemleak.h:43 [inline]
    [<000000002a74b343>] slab_post_alloc_hook mm/slab.h:586 [inline]
    [<000000002a74b343>] slab_alloc mm/slab.c:3319 [inline]
    [<000000002a74b343>] kmem_cache_alloc+0x13f/0x2c0 mm/slab.c:3483
    [<00000000fa370506>] fasync_alloc fs/fcntl.c:895 [inline]
    [<00000000fa370506>] fasync_add_entry fs/fcntl.c:953 [inline]
    [<00000000fa370506>] fasync_helper+0x37/0xa9 fs/fcntl.c:982
    [<000000006c3eaaf1>] sock_fasync+0x4d/0xa0 net/socket.c:1293
    [<0000000098076f55>] ioctl_fioasync fs/ioctl.c:550 [inline]
    [<0000000098076f55>] do_vfs_ioctl+0x409/0x810 fs/ioctl.c:655
    [<00000000df24d2b9>] ksys_ioctl+0x86/0xb0 fs/ioctl.c:713
    [<000000003fec9c80>] __do_sys_ioctl fs/ioctl.c:720 [inline]
    [<000000003fec9c80>] __se_sys_ioctl fs/ioctl.c:718 [inline]
    [<000000003fec9c80>] __x64_sys_ioctl+0x1e/0x30 fs/ioctl.c:718
    [<000000002bebbfe6>] do_syscall_64+0x73/0x1f0  
arch/x86/entry/common.c:290
    [<00000000722d8431>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

BUG: memory leak
unreferenced object 0xffff888128cdf240 (size 48):
  comm "syz-executor670", pid 6990, jiffies 4294952942 (age 13.650s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 01 46 00 00 03 00 00 00  .........F......
    00 00 00 00 00 00 00 00 00 d8 02 19 81 88 ff ff  ................
  backtrace:
    [<000000002a74b343>] kmemleak_alloc_recursive  
include/linux/kmemleak.h:43 [inline]
    [<000000002a74b343>] slab_post_alloc_hook mm/slab.h:586 [inline]
    [<000000002a74b343>] slab_alloc mm/slab.c:3319 [inline]
    [<000000002a74b343>] kmem_cache_alloc+0x13f/0x2c0 mm/slab.c:3483
    [<00000000fa370506>] fasync_alloc fs/fcntl.c:895 [inline]
    [<00000000fa370506>] fasync_add_entry fs/fcntl.c:953 [inline]
    [<00000000fa370506>] fasync_helper+0x37/0xa9 fs/fcntl.c:982
    [<000000006c3eaaf1>] sock_fasync+0x4d/0xa0 net/socket.c:1293
    [<0000000098076f55>] ioctl_fioasync fs/ioctl.c:550 [inline]
    [<0000000098076f55>] do_vfs_ioctl+0x409/0x810 fs/ioctl.c:655
    [<00000000df24d2b9>] ksys_ioctl+0x86/0xb0 fs/ioctl.c:713
    [<000000003fec9c80>] __do_sys_ioctl fs/ioctl.c:720 [inline]
    [<000000003fec9c80>] __se_sys_ioctl fs/ioctl.c:718 [inline]
    [<000000003fec9c80>] __x64_sys_ioctl+0x1e/0x30 fs/ioctl.c:718
    [<000000002bebbfe6>] do_syscall_64+0x73/0x1f0  
arch/x86/entry/common.c:290
    [<00000000722d8431>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

BUG: memory leak
unreferenced object 0xffff888128cdff60 (size 48):
  comm "syz-executor670", pid 6991, jiffies 4294953529 (age 7.780s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 01 46 00 00 03 00 00 00  .........F......
    00 00 00 00 00 00 00 00 00 63 05 1f 81 88 ff ff  .........c......
  backtrace:
    [<000000002a74b343>] kmemleak_alloc_recursive  
include/linux/kmemleak.h:43 [inline]
    [<000000002a74b343>] slab_post_alloc_hook mm/slab.h:586 [inline]
    [<000000002a74b343>] slab_alloc mm/slab.c:3319 [inline]
    [<000000002a74b343>] kmem_cache_alloc+0x13f/0x2c0 mm/slab.c:3483
    [<00000000fa370506>] fasync_alloc fs/fcntl.c:895 [inline]
    [<00000000fa370506>] fasync_add_entry fs/fcntl.c:953 [inline]
    [<00000000fa370506>] fasync_helper+0x37/0xa9 fs/fcntl.c:982
    [<000000006c3eaaf1>] sock_fasync+0x4d/0xa0 net/socket.c:1293
    [<0000000098076f55>] ioctl_fioasync fs/ioctl.c:550 [inline]
    [<0000000098076f55>] do_vfs_ioctl+0x409/0x810 fs/ioctl.c:655
    [<00000000df24d2b9>] ksys_ioctl+0x86/0xb0 fs/ioctl.c:713
    [<000000003fec9c80>] __do_sys_ioctl fs/ioctl.c:720 [inline]
    [<000000003fec9c80>] __se_sys_ioctl fs/ioctl.c:718 [inline]
    [<000000003fec9c80>] __x64_sys_ioctl+0x1e/0x30 fs/ioctl.c:718
    [<000000002bebbfe6>] do_syscall_64+0x73/0x1f0  
arch/x86/entry/common.c:290
    [<00000000722d8431>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



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