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Thu, 15 Jan 2026 20:01:51 -0800 (PST) From: Chaitanya Mishra To: Eddie James Cc: Ninad Palsule , linux-fsi@lists.ozlabs.org, linux-kernel@vger.kernel.org, Chaitanya Mishra Subject: [PATCH v1 1/1] fsi: cfam: clamp chunk length to remaining count Date: Fri, 16 Jan 2026 09:31:40 +0530 Message-ID: <20260116040140.65394-2-chaitanyamishra.ai@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260116040140.65394-1-chaitanyamishra.ai@gmail.com> References: <20260116040140.65394-1-chaitanyamishra.ai@gmail.com> 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" cfam_{read,write} split requests into up to 4-byte aligned chunks. The per-iteration length is computed from the full count and the current alignment. Once total_len advances, this can exceed the remaining bytes, leading to copy_{to,from}_user() touching bytes past the user buffer and advancing the file offset too far. Clamp each chunk to the minimum of the alignment-based length and the remaining bytes so each iteration handles only the bytes left. Fixes: d1dcd6782576 ("fsi: Add cfam char devices") Signed-off-by: Chaitanya Mishra --- drivers/fsi/fsi-core.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c index c6c115993ebc..8a2a02df52ac 100644 --- a/drivers/fsi/fsi-core.c +++ b/drivers/fsi/fsi-core.c @@ -674,8 +674,7 @@ static ssize_t cfam_read(struct file *filep, char __use= r *buf, size_t count, for (total_len =3D 0; total_len < count; total_len +=3D read_len) { __be32 data; =20 - read_len =3D min_t(size_t, count, 4); - read_len -=3D off & 0x3; + read_len =3D min_t(size_t, 4 - (off & 0x3), count - total_len); =20 rc =3D fsi_slave_read(slave, off, &data, read_len); if (rc) @@ -711,8 +710,7 @@ static ssize_t cfam_write(struct file *filep, const cha= r __user *buf, for (total_len =3D 0; total_len < count; total_len +=3D write_len) { __be32 data; =20 - write_len =3D min_t(size_t, count, 4); - write_len -=3D off & 0x3; + write_len =3D min_t(size_t, 4 - (off & 0x3), count - total_len); =20 rc =3D copy_from_user(&data, buf + total_len, write_len); if (rc) { --=20 2.50.1 (Apple Git-155)