From 7ad21dcfeb5181af0c3ee2608808c0c0a5283aa1 Mon Sep 17 00:00:00 2001 From: Bryam Vargas Date: Tue, 16 Jun 2026 23:33:35 -0500 Subject: [PATCH] nfc: fdp: bound the device-reported read length and fix an skb leak fdp_nci_i2c_read() takes the next packet length from two device-supplied bytes and never validates it. The value is a u16 used as the i2c_master_recv() count into a 261-byte on-stack buffer: a malicious, counterfeit or malfunctioning controller (or an i2c bus interposer) can drive it far past the buffer for a stack out-of-bounds write that clobbers the canary and return address, or below the minimum frame size (directly, or by truncating the computed sum) so the header/LRC strip and the next length read run past a short receive. Reject a length outside [FDP_NCI_I2C_MIN_PAYLOAD, FDP_NCI_I2C_MAX_PAYLOAD], as a corrupted packet already is, and force resynchronization. The same loop allocates one data skb per iteration and assumes a length packet followed by a data packet; a device that sends two data packets in one call leaks the first skb when the second allocation overwrites it. Free a previously allocated skb before allocating the next. Fixes: a06347c04c13 ("NFC: Add Intel Fields Peak NFC solution driver") Cc: stable@vger.kernel.org Suggested-by: Simon Horman Signed-off-by: Bryam Vargas Link: https://patch.msgid.link/20260616-b4-disp-b1f8ab4c-v2-1-2d1fe5955325@proton.me Signed-off-by: David Heidelberg --- drivers/nfc/fdp/i2c.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/drivers/nfc/fdp/i2c.c b/drivers/nfc/fdp/i2c.c index c1896a1d978c..f292e7f37456 100644 --- a/drivers/nfc/fdp/i2c.c +++ b/drivers/nfc/fdp/i2c.c @@ -166,9 +166,36 @@ static int fdp_nci_i2c_read(struct fdp_i2c_phy *phy, struct sk_buff **skb) /* Packet that contains a length */ if (tmp[0] == 0 && tmp[1] == 0) { phy->next_read_size = (tmp[2] << 8) + tmp[3] + 3; + + /* + * next_read_size is taken from the device and is used + * as the i2c_master_recv() count for the next packet + * and as the data skb size. A value above the receive + * buffer overflows tmp[]; one below the minimum frame + * size runs the header/LRC strip and the length-field + * read past a short receive. Either way the packet is + * corrupt: drop it and force resynchronization. + */ + if (phy->next_read_size < FDP_NCI_I2C_MIN_PAYLOAD || + phy->next_read_size > FDP_NCI_I2C_MAX_PAYLOAD) { + dev_dbg(&client->dev, "%s: corrupted packet\n", + __func__); + phy->next_read_size = FDP_NCI_I2C_MIN_PAYLOAD; + goto flush; + } } else { phy->next_read_size = FDP_NCI_I2C_MIN_PAYLOAD; + /* + * Only one data packet is delivered per call; if the + * device sends another, do not overwrite and leak the + * skb allocated for the previous one. + */ + if (*skb) { + kfree_skb(*skb); + *skb = NULL; + } + *skb = alloc_skb(len, GFP_KERNEL); if (*skb == NULL) { r = -ENOMEM;