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Date:   Tue, 4 Apr 2023 18:18:30 +0200
From:   Simon Horman <simon.horman@corigine.com>
To:     Eric Dumazet <edumazet@google.com>
Cc:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        eric.dumazet@gmail.com, syzbot <syzkaller@googlegroups.com>,
        Jaewan Kim <jaewan@google.com>,
        Johannes Berg <johannes.berg@intel.com>
Subject: Re: [PATCH net] mac80211_hwsim: fix potential NULL deref in
 hwsim_pmsr_report_nl()
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References: <20230404134803.889673-1-edumazet@google.com>
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On Tue, Apr 04, 2023 at 01:48:03PM +0000, Eric Dumazet wrote:
> syzbot reported a NULL deref caused by a missing check
> in hwsim_pmsr_report_nl(), and bisected the issue to cited commit.
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> CPU: 0 PID: 5084 Comm: syz-executor104 Not tainted 6.3.0-rc4-next-20230331-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
> RIP: 0010:jhash+0x339/0x610 include/linux/jhash.h:95
> Code: 83 fd 01 0f 84 5f ff ff ff eb de 83 fd 05 74 3a e8 ac f5 71 fd 48 8d 7b 05 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 96 02 00 00
> RSP: 0018:ffffc90003abf298 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 0000000000000004 RCX: 0000000000000000
> RDX: 0000000000000001 RSI: ffffffff84111ba4 RDI: 0000000000000009
> RBP: 0000000000000006 R08: 0000000000000005 R09: 000000000000000c
> R10: 0000000000000006 R11: 0000000000000000 R12: 000000004d2c27cd
> R13: 000000002bd9e6c2 R14: 000000002bd9e6c2 R15: 000000002bd9e6c2
> FS: 0000555556847300(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000045ad50 CR3: 0000000078aa6000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> rht_key_hashfn include/linux/rhashtable.h:159 [inline]
> __rhashtable_lookup include/linux/rhashtable.h:604 [inline]
> rhashtable_lookup include/linux/rhashtable.h:646 [inline]
> rhashtable_lookup_fast include/linux/rhashtable.h:672 [inline]
> get_hwsim_data_ref_from_addr+0xb9/0x600 drivers/net/wireless/virtual/mac80211_hwsim.c:757
> hwsim_pmsr_report_nl+0xe7/0xd50 drivers/net/wireless/virtual/mac80211_hwsim.c:3764
> genl_family_rcv_msg_doit.isra.0+0x1e6/0x2d0 net/netlink/genetlink.c:968
> genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]
> genl_rcv_msg+0x4ff/0x7e0 net/netlink/genetlink.c:1065
> netlink_rcv_skb+0x165/0x440 net/netlink/af_netlink.c:2572
> genl_rcv+0x28/0x40 net/netlink/genetlink.c:1076
> netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
> netlink_unicast+0x547/0x7f0 net/netlink/af_netlink.c:1365
> netlink_sendmsg+0x925/0xe30 net/netlink/af_netlink.c:1942
> sock_sendmsg_nosec net/socket.c:724 [inline]
> sock_sendmsg+0xde/0x190 net/socket.c:747
> ____sys_sendmsg+0x71c/0x900 net/socket.c:2501
> ___sys_sendmsg+0x110/0x1b0 net/socket.c:2555
> __sys_sendmsg+0xf7/0x1c0 net/socket.c:2584
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Fixes: 2af3b2a631b1 ("mac80211_hwsim: add PMSR report support via virtio")
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Jaewan Kim <jaewan@google.com>
> Cc: Johannes Berg <johannes.berg@intel.com>

Hi Eric,

I think this is for net-next / wireless-next as
the above mentioned patch does not seem to be in Linus's tree.

> ---
>  drivers/net/wireless/virtual/mac80211_hwsim.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/wireless/virtual/mac80211_hwsim.c b/drivers/net/wireless/virtual/mac80211_hwsim.c
> index f446d8f6e1f6e1df108db00e898fa02970162585..701e14b8e6fe0cae7ee2478c8dff0f2327b54a70 100644
> --- a/drivers/net/wireless/virtual/mac80211_hwsim.c
> +++ b/drivers/net/wireless/virtual/mac80211_hwsim.c
> @@ -3761,6 +3761,8 @@ static int hwsim_pmsr_report_nl(struct sk_buff *msg, struct genl_info *info)
>  	int rem;
>  
>  	src = nla_data(info->attrs[HWSIM_ATTR_ADDR_TRANSMITTER]);
> +	if (!src)
> +		return -EINVAL;
>  	data = get_hwsim_data_ref_from_addr(src);
>  	if (!data)
>  		return -EINVAL;

I could well be wrong, but this looks a little odd given that nla_data is:

static inline void *nla_data(const struct nlattr *nla)
{
        return (char *) nla + NLA_HDRLEN;
}

Perhaps we want something like this (*compile tested only!*) ?

	if (!info->attrs[HWSIM_ATTR_ADDR_TRANSMITTER])
		return -EINVAL;
	src = nla_data(info->attrs[HWSIM_ATTR_ADDR_TRANSMITTER]);
	...