[PATCH] ASoC: SOF: ipc3-dtrace: uninitialized data in dfsentry_trace_filter_write()

[PATCH] ASoC: SOF: ipc3-dtrace: uninitialized data in dfsentry_trace_filter_write()

[Dan Carpenter]

This doesn't check how many bytes the simple_write_to_buffer() writes to
the buffer.  The only thing that we know is that the first byte is
initialized and the last byte of the buffer is set to NUL.  However
the middle bytes could be uninitialized.

There is no need to use simple_write_to_buffer().  This code does not
support partial writes but instead passes "pos = 0" as the starting
offset regardless of what the user passed as "*ppos".  Just use the
copy_from_user() function and initialize the whole buffer.

Fixes: 671e0b90051e ("ASoC: SOF: Clone the trace code to ipc3-dtrace as fw_tracing implementation")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
The nicer thing to do would have been to use strndup_user() but that
comes with a small risk of breaking user space and I can't test this
so I didn't do that.

 sound/soc/sof/ipc3-dtrace.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/sound/soc/sof/ipc3-dtrace.c b/sound/soc/sof/ipc3-dtrace.c
index 1d3bca2d28dd..35da85a45a9a 100644
--- a/sound/soc/sof/ipc3-dtrace.c
+++ b/sound/soc/sof/ipc3-dtrace.c
@@ -186,7 +186,6 @@ static ssize_t dfsentry_trace_filter_write(struct file *file, const char __user
 	struct snd_sof_dfsentry *dfse = file->private_data;
 	struct sof_ipc_trace_filter_elem *elems = NULL;
 	struct snd_sof_dev *sdev = dfse->sdev;
-	loff_t pos = 0;
 	int num_elems;
 	char *string;
 	int ret;
@@ -201,11 +200,11 @@ static ssize_t dfsentry_trace_filter_write(struct file *file, const char __user
 	if (!string)
 		return -ENOMEM;
 
-	/* assert null termination */
-	string[count] = 0;
-	ret = simple_write_to_buffer(string, count, &pos, from, count);
-	if (ret < 0)
+	if (copy_from_user(string, from, count)) {
+		ret = -EFAULT;
 		goto error;
+	}
+	string[count] = '\0';
 
 	ret = trace_filter_parse(sdev, string, &num_elems, &elems);
 	if (ret < 0)
-- 
2.39.2

Re: [PATCH] ASoC: SOF: ipc3-dtrace: uninitialized data in dfsentry_trace_filter_write()

[Mark Brown]

On Fri, 07 Jul 2023 14:25:23 +0300, Dan Carpenter wrote:
> This doesn't check how many bytes the simple_write_to_buffer() writes to
> the buffer.  The only thing that we know is that the first byte is
> initialized and the last byte of the buffer is set to NUL.  However
> the middle bytes could be uninitialized.
> 
> There is no need to use simple_write_to_buffer().  This code does not
> support partial writes but instead passes "pos = 0" as the starting
> offset regardless of what the user passed as "*ppos".  Just use the
> copy_from_user() function and initialize the whole buffer.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[1/1] ASoC: SOF: ipc3-dtrace: uninitialized data in dfsentry_trace_filter_write()
      commit: 469e2f28c2cbee2430058c1c9bb6d1675d7195fb

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark