From: Aleksandr Mishin amishin@t-argos.ru

[ Upstream commit febccb39255f9df35527b88c953b2e0deae50e53 ]

In case of im_protocols value is 1 and tm_protocols value is 0 this combination successfully passes the check 'if (!im_protocols && !tm_protocols)' in the nfc_start_poll(). But then after pn533_poll_create_mod_list() call in pn533_start_poll() poll mod list will remain empty and dev->poll_mod_count will remain 0 which lead to division by zero.

Normally no im protocol has value 1 in the mask, so this combination is not expected by driver. But these protocol values actually come from userspace via Netlink interface (NFC_CMD_START_POLL operation). So a broken or malicious program may pass a message containing a "bad" combination of protocol parameter values so that dev->poll_mod_count is not incremented inside pn533_poll_create_mod_list(), thus leading to division by zero. Call trace looks like: nfc_genl_start_poll() nfc_start_poll() ->start_poll() pn533_start_poll()

Add poll mod list filling check.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: dfccd0f58044 ("NFC: pn533: Add some polling entropy") Signed-off-by: Aleksandr Mishin amishin@t-argos.ru Acked-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Link: https://patch.msgid.link/20240827084822.18785-1-amishin@t-argos.ru Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/nfc/pn533/pn533.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/drivers/nfc/pn533/pn533.c b/drivers/nfc/pn533/pn533.c index b19c39dcfbd9..e2bc67300a91 100644 --- a/drivers/nfc/pn533/pn533.c +++ b/drivers/nfc/pn533/pn533.c @@ -1723,6 +1723,11 @@ static int pn533_start_poll(struct nfc_dev *nfc_dev, }

pn533_poll_create_mod_list(dev, im_protocols, tm_protocols); + if (!dev->poll_mod_count) { + nfc_err(dev->dev, + "Poll mod list is empty\n"); + return -EINVAL; + }

/* Do not always start polling from the same modulation */ get_random_bytes(&rand_mod, sizeof(rand_mod));