Re: [PATCH] net: ipv4: fix memory leak in netlbl_cipsov4_add_std

[Dongliang Mu]

On Tue, Jun 8, 2021 at 9:57 AM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
>
> On Mon, Jun 7, 2021 at 9:19 PM Nanyong Sun <sunnanyong@xxxxxxxxxx> wrote:
> >
> > Reported by syzkaller:
> > BUG: memory leak
> > unreferenced object 0xffff888105df7000 (size 64):
> > comm "syz-executor842", pid 360, jiffies 4294824824 (age 22.546s)
> > hex dump (first 32 bytes):
> > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> > backtrace:
> > [<00000000e67ed558>] kmalloc include/linux/slab.h:590 [inline]
> > [<00000000e67ed558>] kzalloc include/linux/slab.h:720 [inline]
> > [<00000000e67ed558>] netlbl_cipsov4_add_std net/netlabel/netlabel_cipso_v4.c:145 [inline]
> > [<00000000e67ed558>] netlbl_cipsov4_add+0x390/0x2340 net/netlabel/netlabel_cipso_v4.c:416
> > [<0000000006040154>] genl_family_rcv_msg_doit.isra.0+0x20e/0x320 net/netlink/genetlink.c:739
> > [<00000000204d7a1c>] genl_family_rcv_msg net/netlink/genetlink.c:783 [inline]
> > [<00000000204d7a1c>] genl_rcv_msg+0x2bf/0x4f0 net/netlink/genetlink.c:800
> > [<00000000c0d6a995>] netlink_rcv_skb+0x134/0x3d0 net/netlink/af_netlink.c:2504
> > [<00000000d78b9d2c>] genl_rcv+0x24/0x40 net/netlink/genetlink.c:811
> > [<000000009733081b>] netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
> > [<000000009733081b>] netlink_unicast+0x4a0/0x6a0 net/netlink/af_netlink.c:1340
> > [<00000000d5fd43b8>] netlink_sendmsg+0x789/0xc70 net/netlink/af_netlink.c:1929
> > [<000000000a2d1e40>] sock_sendmsg_nosec net/socket.c:654 [inline]
> > [<000000000a2d1e40>] sock_sendmsg+0x139/0x170 net/socket.c:674
> > [<00000000321d1969>] ____sys_sendmsg+0x658/0x7d0 net/socket.c:2350
> > [<00000000964e16bc>] ___sys_sendmsg+0xf8/0x170 net/socket.c:2404
> > [<000000001615e288>] __sys_sendmsg+0xd3/0x190 net/socket.c:2433
> > [<000000004ee8b6a5>] do_syscall_64+0x37/0x90 arch/x86/entry/common.c:47
> > [<00000000171c7cee>] entry_SYSCALL_64_after_hwframe+0x44/0xae
> >
> > The memory of doi_def->map.std pointing is allocated in
> > netlbl_cipsov4_add_std, but no place has freed it. It should be
> > freed in cipso_v4_doi_free which frees the cipso DOI resource.
> >
> > Fixes: 96cb8e3313c7a ("[NetLabel]: CIPSOv4 and Unlabeled packet integration")
> > Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> > Signed-off-by: Nanyong Sun <sunnanyong@xxxxxxxxxx>
> > ---
> >  net/ipv4/cipso_ipv4.c | 1 +
> >  1 file changed, 1 insertion(+)
>
> Nice catch, thanks for fixing this.
>
> Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
>
> > diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
> > index d6e3a92841e3..099259fc826a 100644
> > --- a/net/ipv4/cipso_ipv4.c
> > +++ b/net/ipv4/cipso_ipv4.c
> > @@ -471,6 +471,7 @@ void cipso_v4_doi_free(struct cipso_v4_doi *doi_def)
> >                 kfree(doi_def->map.std->lvl.local);
> >                 kfree(doi_def->map.std->cat.cipso);
> >                 kfree(doi_def->map.std->cat.local);
> > +               kfree(doi_def->map.std);
> >                 break;
> >         }
> >         kfree(doi_def);

Hi kernel developers,

I doubt this patch may cause invalid free in other functions where
map.std is not allocated or initialized, such as
netlbl_cipsov4_add_local, netlbl_cipsov4_add_pass.

Take netlbl_cipsov4_add_pass as an example, any failure after the
doi_def allocation failure will go to cipso_v4_doi_free, and free
doi_def->map.std.

static int netlbl_cipsov4_add_pass(struct genl_info *info,
  struct netlbl_audit *audit_info)
{
int ret_val;
struct cipso_v4_doi *doi_def = NULL;

if (!info->attrs[NLBL_CIPSOV4_A_TAGLST])
return -EINVAL;

doi_def = kmalloc(sizeof(*doi_def), GFP_KERNEL);
if (doi_def == NULL)
return -ENOMEM;
doi_def->type = CIPSO_V4_MAP_PASS;

ret_val = netlbl_cipsov4_add_common(info, doi_def);
if (ret_val != 0)
goto add_pass_failure;

ret_val = cipso_v4_doi_add(doi_def, audit_info);
if (ret_val != 0)
goto add_pass_failure;
return 0;

add_pass_failure:
cipso_v4_doi_free(doi_def);
return ret_val;
}

[1] https://elixir.bootlin.com/linux/latest/source/net/netlabel/netlabel_cipso_v4.c#L326

> > --
> > 2.18.0.huawei.25
>
> --
> paul moore
> www.paul-moore.com