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Sat, 11 Jul 2026 05:36:43 -0700 (PDT) Received: from PeakBook-Mini.tail8e484.ts.net ([178.197.218.188]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47aa0960816sm66169851f8f.29.2026.07.11.05.36.42 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 11 Jul 2026 05:36:43 -0700 (PDT) From: Doruk Tan Ozturk To: david@ixit.cz Cc: oe-linux-nfc@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net] nfc: fdp: bound the device-supplied read size in fdp_nci_i2c_read() Date: Sat, 11 Jul 2026 14:36:41 +0200 Message-ID: <20260711123641.32502-1-doruk@0sec.ai> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" fdp_nci_i2c_read() reads a "length packet" from the FDP I2C controller and computes the size of the next I2C transfer from two device-supplied bytes: phy->next_read_size =3D (tmp[2] << 8) + tmp[3] + 3; next_read_size is a u16 (up to 65535) and is never bounded. On the next loop iteration it is used directly as the length passed to i2c_master_recv(client, tmp, len); which reads into the fixed 261-byte stack buffer tmp[FDP_NCI_I2C_MAX_PAYLOAD]. A malicious or malfunctioning controller that reports a large length thus overflows the stack buffer -- the r !=3D len check runs only after the read has already happened. Reject a next-read size larger than the buffer and resynchronize. Found by 0sec (https://0sec.ai) using automated source analysis; the missing bound is evident from source. Compile-tested. Fixes: a06347c04c13 ("NFC: Add Intel Fields Peak NFC solution driver") Cc: stable@vger.kernel.org Assisted-by: 0sec:claude-opus-4-8 Signed-off-by: Doruk Tan Ozturk --- drivers/nfc/fdp/i2c.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/nfc/fdp/i2c.c b/drivers/nfc/fdp/i2c.c index c1896a1d978c..581f85f0dfa8 100644 --- a/drivers/nfc/fdp/i2c.c +++ b/drivers/nfc/fdp/i2c.c @@ -128,7 +128,7 @@ static const struct nfc_phy_ops i2c_phy_ops =3D { =20 static int fdp_nci_i2c_read(struct fdp_i2c_phy *phy, struct sk_buff **skb) { - int r, len; + int r =3D -EREMOTEIO, len; u8 tmp[FDP_NCI_I2C_MAX_PAYLOAD], lrc, k; u16 i; struct i2c_client *client =3D phy->i2c_dev; @@ -140,6 +140,13 @@ static int fdp_nci_i2c_read(struct fdp_i2c_phy *phy, s= truct sk_buff **skb) =20 len =3D phy->next_read_size; =20 + if (len > FDP_NCI_I2C_MAX_PAYLOAD) { + dev_dbg(&client->dev, "%s: read size %d too large\n", + __func__, len); + phy->next_read_size =3D FDP_NCI_I2C_MIN_PAYLOAD; + goto flush; + } + r =3D i2c_master_recv(client, tmp, len); if (r !=3D len) { dev_dbg(&client->dev, "%s: i2c recv err: %d\n", --=20 2.43.0