pdfiumload: guard against `NULL`-bitmaps #4599

zhifengzhuang · 2025-07-04T08:42:52Z

Fix pdfiumload.c vips_foreign_load_pdf_generate(). Inconsistent PDF page dimensions (varying width/height) may generate empty Bitmaps, leading to crashes in PDFium versions prior to 6633.
We could reproduce using the pdf
052201055248624de6f3063354544793.pdf
: vips pdfload 052201055248624de6f3063354544793.pdf out.jpeg --n=-1 --dpi=180

Draw a background color on outRegion to maintain consistency with Poppler's rendering behavior.

kleisauke · 2025-07-04T08:58:46Z

Fix pdfiumload.c vips_foreign_load_pdf_generate(). Inconsistent PDF page dimensions (varying width/height) may generate empty Bitmaps, leading to crashes in PDFium versions prior to 6633.

I wonder if commit 2fdab9b is also related here.

Draw a background color on outRegion to maintain consistency with Poppler's rendering behavior.

This effectively reverts commit 985fb1d, I'm not sure if that's wanted.

zhifengzhuang · 2025-07-04T09:29:07Z

Commit 2fdab9b seems not to related here. Older pdfium(<6633) will crash when an empty bitmap pass to FPDF_FFLDraw. We should check the rect width&height before we call FPDF_FFLDraw?
Commit 985fb1d seems to related here. When there is no overlapping area between the VipsRegion and the PDF, actively draw the background color to ensure the PDFium output matches that of Poppler.

jcupitt · 2025-07-05T10:14:56Z

Hi @zhifengzhuang, thank you for this PR!

I wonder if commit 2fdab9b is also related here.

I think that's unrelated -- this PR fixes the case where you have a narrow page and the tilecache asks for a rect outside the page boundary.

poppler deals with this gracefully, but (as @zhifengzhuang says) older pdfiums will crash.

This effectively reverts commit 985fb1d, I'm not sure if that's wanted.

I agree, I'm not sure about the change to background. I think this is a case where PDFium has better transparency support than poppler, so we don't want to match the behaviour exactly.

jcupitt · 2025-07-05T10:16:16Z

libvips/foreign/pdfiumload.c

+    /*
+     * Same with popperload
+     */
+    vips_region_paint_pel(out_region, r, pdf->ink);


I don't think we should do this. We set the background when required with FPDFBitmap_FillRect() below.

I don't think we should do this. We set the background when required with FPDFBitmap_FillRect() below.

So maybe we could paint background color to out_region when rect is empty?

jcupitt · 2025-07-05T10:20:54Z

libvips/foreign/pdfiumload.c

@@ -592,39 +597,43 @@ vips_foreign_load_pdf_generate(VipsRegion *out_region,
 		if (vips_foreign_load_pdf_get_page(pdf, pdf->page_no + i))


This could move inside the rect size test if(), eg.:

top = r->top; while (top < VIPS_RECT_BOTTOM(r)) { 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; 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)); ... etc

kleisauke · 2025-07-06T14:18:36Z

I can confirm that this issue reproduces with PDFium 6611 but does not occur with PDFium 6666. Tested using:

Details

# export PDFIUM_VERSION=6666
export PDFIUM_VERSION=6611
mkdir -p $HOME/pdfium-linux-x64/lib/pkgconfig
curl -Ls https://github.com/bblanchon/pdfium-binaries/releases/download/chromium%2F$PDFIUM_VERSION/pdfium-linux-x64.tgz | tar xzC $HOME/pdfium-linux-x64
cat > $HOME/pdfium-linux-x64/lib/pkgconfig/pdfium.pc << EOF
prefix=$HOME/pdfium-linux-x64
exec_prefix=\${prefix}
libdir=\${exec_prefix}/lib
includedir=\${prefix}/include

Name: pdfium
Description: PDFium
Version: $PDFIUM_VERSION
Libs: -L\${libdir} -lpdfium
Cflags: -I\${includedir}
EOF

export PKG_CONFIG_PATH=$HOME/pdfium-linux-x64/lib/pkgconfig${PKG_CONFIG_PATH:+:$PKG_CONFIG_PATH}
export LD_LIBRARY_PATH=$HOME/pdfium-linux-x64/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
pkg-config --exists --print-errors "pdfium >= 4200" && echo OK

meson setup build --prefix=/usr -Ddeprecated=false -Dexamples=false -Dintrospection=disabled
meson compile -Cbuild
sudo meson install -Cbuild

It looks like this was fixed with commit https://pdfium.googlesource.com/pdfium/+/f8e68068d9301f24993afd94c270860dc0244674, i.e. this diff:

@@ -696,8 +727,13 @@ FPDF_EXPORT void FPDF_CALLCONV FPDF_FFLDraw(FPDF_FORMHANDLE hHandle,
                                             int size_y,
                                             int rotate,
                                             int flags) {
-  FFLCommon(hHandle, bitmap, nullptr, page, start_x, start_y, size_x, size_y,
-            rotate, flags);
+  CFX_DIBitmap* cbitmap = CFXDIBitmapFromFPDFBitmap(bitmap);
+  if (!cbitmap) {
+    return;
+  }
+
+  FFLCommon(hHandle, page, cbitmap, start_x, start_y, size_x, size_y, rotate,
+            flags);
 }
 
 #if defined(PDF_USE_SKIA)

Which ensures NULL bitmaps are handled gracefully in FPDF_FFLDraw().

zhifengzhuang · 2025-07-07T04:05:02Z

Thanks for replying. I remove vips_region_paint_pel and update test if().

zhifengzhuang · 2025-07-07T05:56:22Z

I can confirm that this issue reproduces with PDFium 6611 but does not occur with PDFium 6666. Tested using:

Details
It looks like this was fixed with commit https://pdfium.googlesource.com/pdfium/+/f8e68068d9301f24993afd94c270860dc0244674, i.e. this diff:
@@ -696,8 +727,13 @@ FPDF_EXPORT void FPDF_CALLCONV FPDF_FFLDraw(FPDF_FORMHANDLE hHandle,
                                             int size_y,
                                             int rotate,
                                             int flags) {
-  FFLCommon(hHandle, bitmap, nullptr, page, start_x, start_y, size_x, size_y,
-            rotate, flags);
+  CFX_DIBitmap* cbitmap = CFXDIBitmapFromFPDFBitmap(bitmap);
+  if (!cbitmap) {
+    return;
+  }
+
+  FFLCommon(hHandle, page, cbitmap, start_x, start_y, size_x, size_y, rotate,
+            flags);
 }
 
 #if defined(PDF_USE_SKIA)
Which ensures NULL bitmaps are handled gracefully in FPDF_FFLDraw().

Yes，it was fixed https://pdfium.googlesource.com/pdfium/+/f8e68068d9301f24993afd94c270860dc0244674 (Just between 6632 & 6633)

kleisauke · 2025-07-07T09:24:07Z

I've updated this PR to target the 8.17 branch and revised the commit message and changelog note accordingly.

libvips/foreign/pdfiumload.c

Co-authored-by: Kleis Auke Wolthuizen <github@kleisauke.nl>

jcupitt · 2025-07-07T12:53:12Z

Great! Let's merge!

Thank you for doing this work, @zhifengzhuang, this is a good thing to fix. This change will be in libvips 8.17.1.

jcupitt reviewed Jul 5, 2025

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kleisauke mentioned this pull request Jul 6, 2025

Update ChangeLog ahead of v8.17.1 #4603

Merged

zhifengzhuang force-pushed the master branch 2 times, most recently from 7f8f74d to 13eef6f Compare July 7, 2025 04:04

zhifengzhuang force-pushed the master branch 2 times, most recently from b45bf87 to 6977e1e Compare July 7, 2025 06:17

kleisauke force-pushed the master branch from 6977e1e to 849dcca Compare July 7, 2025 09:23

kleisauke changed the base branch from master to 8.17 July 7, 2025 09:23

kleisauke changed the title ~~Fix pdfiumload.c vips_foreign_load_pdf_generate()~~ pdfiumload: guard against NULL-bitmaps Jul 7, 2025

jcupitt reviewed Jul 7, 2025

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pdfiumload: guard against NULL-bitmaps

8267cd3

zhifengzhuang force-pushed the master branch from 849dcca to 8267cd3 Compare July 7, 2025 11:54

kleisauke reviewed Jul 7, 2025

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libvips/foreign/pdfiumload.c Outdated Show resolved Hide resolved

Update libvips/foreign/pdfiumload.c

4189938

Co-authored-by: Kleis Auke Wolthuizen <github@kleisauke.nl>

jcupitt merged commit 122e572 into libvips:8.17 Jul 7, 2025
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		@@ -592,39 +597,43 @@ vips_foreign_load_pdf_generate(VipsRegion *out_region,
		if (vips_foreign_load_pdf_get_page(pdf, pdf->page_no + i))

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