Re: memory leak in nf_hook_entries_grow

[Julian Anastasov]

	Hello,

On Mon, 3 Jun 2019, syzbot wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    3ab4436f Merge tag 'nfsd-5.2-1' of git://linux-nfs.org/~bf..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15feaf82a00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=50393f7bfe444ff6
> dashboard link: https://syzkaller.appspot.com/bug?extid=722da59ccb264bc19910
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12f02772a00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1657b80ea00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+722da59ccb264bc19910@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> 035][ T7273] IPVS: ftp: loaded support on port[0] = 21
> BUG: memory leak
> unreferenced object 0xffff88810acd8a80 (size 96):
>  comm "syz-executor073", pid 7254, jiffies 4294950560 (age 22.250s)
>  hex dump (first 32 bytes):
>    02 00 00 00 00 00 00 00 50 8b bb 82 ff ff ff ff  ........P.......
>    00 00 00 00 00 00 00 00 00 77 bb 82 ff ff ff ff  .........w......
>  backtrace:
>    [<0000000013db61f1>] kmemleak_alloc_recursive include/linux/kmemleak.h:55
>    [inline]
>    [<0000000013db61f1>] slab_post_alloc_hook mm/slab.h:439 [inline]
>    [<0000000013db61f1>] slab_alloc_node mm/slab.c:3269 [inline]
>    [<0000000013db61f1>] kmem_cache_alloc_node_trace+0x15b/0x2a0 mm/slab.c:3597
>    [<000000001a27307d>] __do_kmalloc_node mm/slab.c:3619 [inline]
>    [<000000001a27307d>] __kmalloc_node+0x38/0x50 mm/slab.c:3627
>    [<0000000025054add>] kmalloc_node include/linux/slab.h:590 [inline]
>    [<0000000025054add>] kvmalloc_node+0x4a/0xd0 mm/util.c:431
>    [<0000000050d1bc00>] kvmalloc include/linux/mm.h:637 [inline]
>    [<0000000050d1bc00>] kvzalloc include/linux/mm.h:645 [inline]
>    [<0000000050d1bc00>] allocate_hook_entries_size+0x3b/0x60
>    net/netfilter/core.c:61
>    [<00000000e8abe142>] nf_hook_entries_grow+0xae/0x270
>    net/netfilter/core.c:128
>    [<000000004b94797c>] __nf_register_net_hook+0x9a/0x170
>    net/netfilter/core.c:337
>    [<00000000d1545cbc>] nf_register_net_hook+0x34/0xc0
>    net/netfilter/core.c:464
>    [<00000000876c9b55>] nf_register_net_hooks+0x53/0xc0
>    net/netfilter/core.c:480
>    [<000000002ea868e0>] __ip_vs_init+0xe8/0x170
>    net/netfilter/ipvs/ip_vs_core.c:2280

	After commit "ipvs: Fix use-after-free in ip_vs_in" we planned
to call nf_register_net_hooks() only when rule is created but this
is net-next material and we should not leave leak in the error path.
I'll post a patch that adds .init handler for ipvs_core_dev_ops, so
that nf_register_net_hooks() is called there.

> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
> 
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> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

Regards

--
Julian Anastasov <ja@xxxxxx>