[PATCH net v2] nfc: pn533: Clear nfc_target before being used

[Minsuk Kang <linuxlovemin@yonsei.ac.kr>]

Fix a slab-out-of-bounds read that occurs in nla_put() called from
nfc_genl_send_target() when target->sensb_res_len, which is duplicated
from an nfc_target in pn533, is too large as the nfc_target is not
properly initialized and retains garbage values. Clear nfc_targets with
memset() before they are used.

Found by a modified version of syzkaller.

BUG: KASAN: slab-out-of-bounds in nla_put
Call Trace:
 memcpy
 nla_put
 nfc_genl_dump_targets
 genl_lock_dumpit
 netlink_dump
 __netlink_dump_start
 genl_family_rcv_msg_dumpit
 genl_rcv_msg
 netlink_rcv_skb
 genl_rcv
 netlink_unicast
 netlink_sendmsg
 sock_sendmsg
 ____sys_sendmsg
 ___sys_sendmsg
 __sys_sendmsg
 do_syscall_64

Fixes: 673088fb42d0 ("NFC: pn533: Send ATR_REQ directly for active device detection")
Fixes: 361f3cb7f9cf ("NFC: DEP link hook implementation for pn533")
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Minsuk Kang <linuxlovemin@yonsei.ac.kr>
---
v1->v2:
  Clear another nfc_target in pn533_in_dep_link_up_complete()
  Fix the commit message

 drivers/nfc/pn533/pn533.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/nfc/pn533/pn533.c b/drivers/nfc/pn533/pn533.c
index d9f6367b9993..f0cac1900552 100644
--- a/drivers/nfc/pn533/pn533.c
+++ b/drivers/nfc/pn533/pn533.c
@@ -1295,6 +1295,8 @@ static int pn533_poll_dep_complete(struct pn533 *dev, void *arg,
 	if (IS_ERR(resp))
 		return PTR_ERR(resp);
 
+	memset(&nfc_target, 0, sizeof(struct nfc_target));
+
 	rsp = (struct pn533_cmd_jump_dep_response *)resp->data;
 
 	rc = rsp->status & PN533_CMD_RET_MASK;
@@ -1926,6 +1928,8 @@ static int pn533_in_dep_link_up_complete(struct pn533 *dev, void *arg,
 
 		dev_dbg(dev->dev, "Creating new target\n");
 
+		memset(&nfc_target, 0, sizeof(struct nfc_target));
+
 		nfc_target.supported_protocols = NFC_PROTO_NFC_DEP_MASK;
 		nfc_target.nfcid1_len = 10;
 		memcpy(nfc_target.nfcid1, rsp->nfcid3t, nfc_target.nfcid1_len);
-- 
2.25.1