media: staging/intel-ipu3: Fix set_fmt error handling

If there in an error during a set_fmt, do not overwrite the previous
sizes with the invalid config.

Without this patch, v4l2-compliance ends up allocating 4GiB of RAM and
causing the following OOPs

[   38.662975] ipu3-imgu 0000:00:05.0: swiotlb buffer is full (sz: 4096 bytes)
[   38.662980] DMA: Out of SW-IOMMU space for 4096 bytes at device 0000:00:05.0
[   38.663010] general protection fault: 0000 [#1] PREEMPT SMP

Cc: [email protected]
Fixes: 6d5f26f ("media: staging/intel-ipu3-v4l: reduce kernel stack usage")
Signed-off-by: Ricardo Ribalda <[email protected]>
Signed-off-by: Sakari Ailus <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>

drivers/staging/media/ipu3/ipu3-v4l2.c

@@ -669,6 +669,7 @@ static int imgu_fmt(struct imgu_device *imgu, unsigned int pipe, int node,
 	struct imgu_css_pipe *css_pipe = &imgu->css.pipes[pipe];
 	struct imgu_media_pipe *imgu_pipe = &imgu->imgu_pipe[pipe];
 	struct imgu_v4l2_subdev *imgu_sd = &imgu_pipe->imgu_sd;
+	struct v4l2_pix_format_mplane fmt_backup;
 
 	dev_dbg(dev, "set fmt node [%u][%u](try = %u)", pipe, node, try);
 
@@ -734,13 +735,17 @@ static int imgu_fmt(struct imgu_device *imgu, unsigned int pipe, int node,
 		ret = -EINVAL;
 		goto out;
 	}
+	fmt_backup = *fmts[css_q];
 	*fmts[css_q] = f->fmt.pix_mp;
 
 	if (try)
 		ret = imgu_css_fmt_try(&imgu->css, fmts, rects, pipe);
 	else
 		ret = imgu_css_fmt_set(&imgu->css, fmts, rects, pipe);
 
+	if (try || ret < 0)
+		*fmts[css_q] = fmt_backup;
+
 	/* ret is the binary number in the firmware blob */
 	if (ret < 0)
 		goto out;