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Message-ID: <bc5c070e-4e9f-2bc2-ed07-788b29117143@linaro.org>
Date: Mon, 5 Dec 2022 08:57:48 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Kees Cook <keescook@...omium.org>
Cc: syzbot <syzbot+210e196cef4711b65139@...kaller.appspotmail.com>,
davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] WARNING in nci_add_new_protocol
On 02/12/2022 22:36, Kees Cook wrote:
> On Sun, Nov 27, 2022 at 02:26:30PM -0800, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: 4312098baf37 Merge tag 'spi-fix-v6.1-rc6' of git://git.ker..
>> git tree: upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=12e25bb5880000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=b1129081024ee340
>> dashboard link: https://syzkaller.appspot.com/bug?extid=210e196cef4711b65139
>> compiler: arm-linux-gnueabi-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> userspace arch: arm
>>
>> Unfortunately, I don't have any reproducer for this issue yet.
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+210e196cef4711b65139@...kaller.appspotmail.com
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 7843 at net/nfc/nci/ntf.c:260 nci_add_new_protocol+0x268/0x30c net/nfc/nci/ntf.c:260
>> memcpy: detected field-spanning write (size 129) of single field "target->sensf_res" at net/nfc/nci/ntf.c:260 (size 18)
>
> This looks like a legitimate overflow flaw to me. Likely introduced with
> commit 019c4fbaa790 ("NFC: Add NCI multiple targets support").
>
> These appear to be explicitly filling fixed-size arrays:
>
> struct nfc_target {
> u32 idx;
> u32 supported_protocols;
> u16 sens_res;
> u8 sel_res;
> u8 nfcid1_len;
> u8 nfcid1[NFC_NFCID1_MAXSIZE];
> u8 nfcid2_len;
> u8 nfcid2[NFC_NFCID2_MAXSIZE];
> u8 sensb_res_len;
> u8 sensb_res[NFC_SENSB_RES_MAXSIZE];
> u8 sensf_res_len;
> u8 sensf_res[NFC_SENSF_RES_MAXSIZE];
> u8 hci_reader_gate;
> u8 logical_idx;
> u8 is_iso15693;
> u8 iso15693_dsfid;
> u8 iso15693_uid[NFC_ISO15693_UID_MAXSIZE];
> };
>
> static int nci_add_new_protocol(..., struct nfc_target *target, ...)
> {
> ...
> } else if (rf_tech_and_mode == NCI_NFC_B_PASSIVE_POLL_MODE) {
> nfcb_poll = (struct rf_tech_specific_params_nfcb_poll *)params;
>
> target->sensb_res_len = nfcb_poll->sensb_res_len;
> if (target->sensb_res_len > 0) {
> memcpy(target->sensb_res, nfcb_poll->sensb_res,
> target->sensb_res_len);
> }
> } else if (rf_tech_and_mode == NCI_NFC_F_PASSIVE_POLL_MODE) {
> nfcf_poll = (struct rf_tech_specific_params_nfcf_poll *)params;
>
> target->sensf_res_len = nfcf_poll->sensf_res_len;
> if (target->sensf_res_len > 0) {
> memcpy(target->sensf_res, nfcf_poll->sensf_res,
> target->sensf_res_len);
> }
> } else if (rf_tech_and_mode == NCI_NFC_V_PASSIVE_POLL_MODE) {
> nfcv_poll = (struct rf_tech_specific_params_nfcv_poll *)params;
>
> target->is_iso15693 = 1;
> target->iso15693_dsfid = nfcv_poll->dsfid;
> memcpy(target->iso15693_uid, nfcv_poll->uid, NFC_ISO15693_UID_MAXSIZE);
> }
> ...
>
> But the sizes are unbounds-checked, which means the buffers can be
> overwritten (as seen with the syzkaller report).
>
> Perhaps this to fix it?
>
> diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c
> index 282c51051dcc..3a79f07bfea7 100644
> --- a/net/nfc/nci/ntf.c
> +++ b/net/nfc/nci/ntf.c
> @@ -240,6 +240,8 @@ static int nci_add_new_protocol(struct nci_dev *ndev,
> target->sens_res = nfca_poll->sens_res;
> target->sel_res = nfca_poll->sel_res;
> target->nfcid1_len = nfca_poll->nfcid1_len;
> + if (target->nfcid1_len > ARRAY_SIZE(target->target->nfcid1))
> + return -EPROTO;
Or truncate (copy up to size of array) but both solutions look fine to me.
>
Best regards,
Krzysztof
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