pdfiumload: guard against NULL-bitmaps (#4599)

zhifengzhuang · daniel.zhuang · jcupitt · web-flow · commit 122e57227636 · 2025-07-07T13:52:20.000+01:00
* pdfiumload: guard against `NULL`-bitmaps

* Update libvips/foreign/pdfiumload.c

Co-authored-by: Kleis Auke Wolthuizen &lt;github@kleisauke.nl&gt;

---------

Co-authored-by: daniel.zhuang &lt;zhuangzengfeng@gmail.com&gt;
Co-authored-by: John Cupitt &lt;jcupitt@gmail.com&gt;
Co-authored-by: Kleis Auke Wolthuizen &lt;github@kleisauke.nl&gt;
diff --git a/ChangeLog b/ChangeLog
@@ -10,6 +10,7 @@ master
 - tiffsave: always apply resolution unit conversion [kleisauke]
 - cache: suppress invalidation errors in release builds [kleisauke]
 - dzsave: IIIF: use named region of 'full' when no crop takes place [lovell]
+- pdfload: fix potential crash with pdfium < 6633 [zhifengzhuang]
 
 5/6/25 8.17.0
 
diff --git a/libvips/foreign/pdfiumload.c b/libvips/foreign/pdfiumload.c
@@ -584,47 +584,53 @@ vips_foreign_load_pdf_generate(VipsRegion *out_region,
 
 	top = r->top;
 	while (top < VIPS_RECT_BOTTOM(r)) {
-		VipsRect rect;
 		FPDF_BITMAP bitmap;
 
+		/* Is the rect within this page? It might not be if the output is more
+		 * than one tile wide and this page is narrower.
+		 */
+		VipsRect rect;
 		vips_rect_intersectrect(r, &pdf->pages[i], &rect);
+		if (rect.width > 0 &&
+			rect.height > 0) {
 
-		if (vips_foreign_load_pdf_get_page(pdf, pdf->page_no + i))
-			return -1;
+			if (vips_foreign_load_pdf_get_page(pdf, pdf->page_no + i))
+				return -1;
 
-		vips__worker_lock(&vips_pdfium_mutex);
+			vips__worker_lock(&vips_pdfium_mutex);
 
-		/* 4 means RGBA.
-		 */
-		bitmap = FPDFBitmap_CreateEx(rect.width, rect.height, 4,
-			VIPS_REGION_ADDR(out_region, rect.left, rect.top),
-			VIPS_REGION_LSKIP(out_region));
+			/* 4 means RGBA.
+			 */
+			bitmap = FPDFBitmap_CreateEx(rect.width, rect.height, 4,
+				VIPS_REGION_ADDR(out_region, rect.left, rect.top),
+				VIPS_REGION_LSKIP(out_region));
 
-		/* Only paint the background if there's no transparency.
-		 */
-		if (!FPDFPage_HasTransparency(pdf->page)) {
-			FPDF_DWORD ink = *((guint32 *) pdf->ink);
+			/* Only paint the background if there's no transparency.
+			 */
+			if (!FPDFPage_HasTransparency(pdf->page)) {
+				FPDF_DWORD ink = *((guint32 *) pdf->ink);
 
-			FPDFBitmap_FillRect(bitmap,
-				0, 0, rect.width, rect.height, ink);
-		}
+				FPDFBitmap_FillRect(bitmap,
+					0, 0, rect.width, rect.height, ink);
+			}
 
-		// pdfium writes bgra by default, we need rgba
-		FPDF_RenderPageBitmap(bitmap, pdf->page,
-			pdf->pages[i].left - rect.left,
-			pdf->pages[i].top - rect.top,
-			pdf->pages[i].width, pdf->pages[i].height,
-			0, FPDF_ANNOT | FPDF_REVERSE_BYTE_ORDER);
+			// pdfium writes bgra by default, we need rgba
+			FPDF_RenderPageBitmap(bitmap, pdf->page,
+				pdf->pages[i].left - rect.left,
+				pdf->pages[i].top - rect.top,
+				pdf->pages[i].width, pdf->pages[i].height,
+				0, FPDF_ANNOT | FPDF_REVERSE_BYTE_ORDER);
 
-		FPDF_FFLDraw(pdf->form, bitmap, pdf->page,
-			pdf->pages[i].left - rect.left,
-			pdf->pages[i].top - rect.top,
-			pdf->pages[i].width, pdf->pages[i].height,
-			0, FPDF_ANNOT | FPDF_REVERSE_BYTE_ORDER);
+			FPDF_FFLDraw(pdf->form, bitmap, pdf->page,
+				pdf->pages[i].left - rect.left,
+				pdf->pages[i].top - rect.top,
+				pdf->pages[i].width, pdf->pages[i].height,
+				0, FPDF_ANNOT | FPDF_REVERSE_BYTE_ORDER);
 
-		FPDFBitmap_Destroy(bitmap);
+			FPDFBitmap_Destroy(bitmap);
 
-		g_mutex_unlock(&vips_pdfium_mutex);
+			g_mutex_unlock(&vips_pdfium_mutex);
+		}
 
 		top += rect.height;
 		i += 1;
