Commit 978d2813 authored by Miaoqian Lin's avatar Miaoqian Lin Committed by Jonathan Cameron
Browse files

iio: dac: ad3552r-hs: fix out-of-bound write in ad3552r_hs_write_data_source 



When simple_write_to_buffer() succeeds, it returns the number of bytes
actually copied to the buffer. The code incorrectly uses 'count'
as the index for null termination instead of the actual bytes copied.
If count exceeds the buffer size, this leads to out-of-bounds write.
Add a check for the count and use the return value as the index.

The bug was validated using a demo module that mirrors the original
code and was tested under QEMU.

Pattern of the bug:
- A fixed 64-byte stack buffer is filled using count.
- If count > 64, the code still does buf[count] = '\0', causing an
- out-of-bounds write on the stack.

Steps for reproduce:
- Opens the device node.
- Writes 128 bytes of A to it.
- This overflows the 64-byte stack buffer and KASAN reports the OOB.

Found via static analysis. This is similar to the
commit da937481 ("iio: backend: fix out-of-bound write")

Fixes: b1c5d68e ("iio: dac: ad3552r-hs: add support for internal ramp")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarMiaoqian Lin <linmq006@gmail.com>
Reviewed-by: default avatarNuno Sá <nuno.sa@analog.com>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: default avatarDavid Lechner <dlechner@baylibre.com>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent b8f15d1d

drivers/iio/dac/ad3552r-hs.c

+4 −1
Original line number Diff line number Diff line
@@ -549,12 +549,15 @@ static ssize_t ad3552r_hs_write_data_source(struct file *f, 


	guard(mutex)(&st->lock);



	if (count >= sizeof(buf))

		return -ENOSPC;



	ret = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf,

				     count);

	if (ret < 0)

		return ret;



	buf[count] = '\0';

	buf[ret] = '\0';



	ret = match_string(dbgfs_attr_source, ARRAY_SIZE(dbgfs_attr_source),

			   buf);