From 9120a247436e84c0b4eea828cb11e8f665fcde30 Mon Sep 17 00:00:00 2001
From: DRC <information@libjpeg-turbo.org>
Date: Thu, 23 Jul 2020 21:24:38 -0500
Subject: [PATCH] Fix jpeg_skip_scanlines() segfault w/merged upsamp

The additional segfault mentioned in #244 was due to the fact that
the merged upsamplers use a different private structure than the
non-merged upsamplers.  jpeg_skip_scanlines() was assuming the latter, so
when merged upsampling was enabled, jpeg_skip_scanlines() clobbered one
of the IDCT method pointers in the merged upsampler's private structure.

For reasons unknown, the test image in #441 did not encounter this
segfault (too small?), but it encountered an issue similar to the one
fixed in 5bc43c7821df982f65aa1c738f67fbf7cba8bd69, whereby it was
necessary to set up a dummy postprocessing function in
read_and_discard_scanlines() when merged upsampling was enabled.
Failing to do so caused either a segfault in merged_2v_upsample() (due
to a NULL pointer being passed to jcopy_sample_rows()) or an error
("Corrupt JPEG data: premature end of data segment"), depending on the
number of scanlines skipped and whether the first scanline skipped was
an odd- or even-numbered row.

Fixes #441
Fixes #244 (for real this time)
---
 jdapistd.c   | 72 ++++++++++++++++++++++++++++++++++++++++++++++------
 jdmerge.c    | 46 +++++++--------------------------
 jdmerge.h    | 47 ++++++++++++++++++++++++++++++++++
 jdmrg565.c   | 10 ++++----
 jdmrgext.c   |  6 ++---
 6 files changed, 134 insertions(+), 53 deletions(-)
 create mode 100644 jdmerge.h

diff --git a/jdapistd.c b/jdapistd.c
index 2c808fa56..91da642da 100644
--- a/jdapistd.c
+++ b/jdapistd.c
@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2010, 2015-2018, D. R. Commander.
+ * Copyright (C) 2010, 2015-2018, 2020, D. R. Commander.
  * Copyright (C) 2015, Google, Inc.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
@@ -21,6 +21,8 @@
 #include "jinclude.h"
 #include "jdmainct.h"
 #include "jdcoefct.h"
+#include "jdmaster.h"
+#include "jdmerge.h"
 #include "jdsample.h"
 #include "jmemsys.h"
 
@@ -304,6 +306,16 @@ noop_quantize(j_decompress_ptr cinfo, JSAMPARRAY input_buf,
 }
 
 
+/* Dummy postprocessing function used by jpeg_skip_scanlines() */
+LOCAL(void)
+noop_post_process (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
+                   JDIMENSION *in_row_group_ctr,
+                   JDIMENSION in_row_groups_avail, JSAMPARRAY output_buf,
+                   JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
+{
+}
+
+
 /*
  * In some cases, it is best to call jpeg_read_scanlines() and discard the
  * output, rather than skipping the scanlines, because this allows us to
@@ -316,11 +328,17 @@ LOCAL(void)
 read_and_discard_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
 {
   JDIMENSION n;
+  my_master_ptr master = (my_master_ptr)cinfo->master;
   void (*color_convert) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                          JDIMENSION input_row, JSAMPARRAY output_buf,
                          int num_rows) = NULL;
   void (*color_quantize) (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
                           JSAMPARRAY output_buf, int num_rows) = NULL;
+  void (*post_process_data) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
+                             JDIMENSION *in_row_group_ctr,
+                             JDIMENSION in_row_groups_avail,
+                             JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
+                             JDIMENSION out_rows_avail) = NULL;
 
   if (cinfo->cconvert && cinfo->cconvert->color_convert) {
     color_convert = cinfo->cconvert->color_convert;
@@ -332,6 +350,12 @@ read_and_discard_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
     cinfo->cquantize->color_quantize = noop_quantize;
   }
 
+  if (master->using_merged_upsample && cinfo->post &&
+      cinfo->post->post_process_data) {
+    post_process_data = cinfo->post->post_process_data;
+    cinfo->post->post_process_data = noop_post_process;
+  }
+
   for (n = 0; n < num_lines; n++)
     jpeg_read_scanlines(cinfo, NULL, 1);
 
@@ -340,6 +364,9 @@ read_and_discard_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
 
   if (color_quantize)
     cinfo->cquantize->color_quantize = color_quantize;
+
+  if (post_process_data)
+    cinfo->post->post_process_data = post_process_data;
 }
 
 
@@ -382,7 +409,7 @@ jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
 {
   my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_master_ptr master = (my_master_ptr)cinfo->master;
   JDIMENSION i, x;
   int y;
   JDIMENSION lines_per_iMCU_row, lines_left_in_iMCU_row, lines_after_iMCU_row;
@@ -445,8 +472,16 @@ jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
     main_ptr->buffer_full = FALSE;
     main_ptr->rowgroup_ctr = 0;
     main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
-    upsample->next_row_out = cinfo->max_v_samp_factor;
-    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+    if (master->using_merged_upsample) {
+      my_merged_upsample_ptr upsample =
+        (my_merged_upsample_ptr)cinfo->upsample;
+      upsample->spare_full = FALSE;
+      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+    } else {
+      my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+      upsample->next_row_out = cinfo->max_v_samp_factor;
+      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+    }
   }
 
   /* Skipping is much simpler when context rows are not required. */
@@ -458,8 +493,16 @@ jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
       cinfo->output_scanline += lines_left_in_iMCU_row;
       main_ptr->buffer_full = FALSE;
       main_ptr->rowgroup_ctr = 0;
-      upsample->next_row_out = cinfo->max_v_samp_factor;
-      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+      if (master->using_merged_upsample) {
+        my_merged_upsample_ptr upsample =
+          (my_merged_upsample_ptr)cinfo->upsample;
+        upsample->spare_full = FALSE;
+        upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+      } else {
+        my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+        upsample->next_row_out = cinfo->max_v_samp_factor;
+        upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+      }
     }
   }
 
@@ -494,7 +537,14 @@ jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
       cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
       increment_simple_rowgroup_ctr(cinfo, lines_to_read);
     }
-    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+    if (master->using_merged_upsample) {
+      my_merged_upsample_ptr upsample =
+        (my_merged_upsample_ptr)cinfo->upsample;
+      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+    } else {
+      my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+    }
     return num_lines;
   }
 
@@ -535,7 +585,13 @@ jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
    * bit odd, since "rows_to_go" seems to be redundantly keeping track of
    * output_scanline.
    */
-  upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+  if (master->using_merged_upsample) {
+    my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
+    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+  } else {
+    my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
+  }
 
   /* Always skip the requested number of lines. */
   return num_lines;
diff --git a/jdmerge.c b/jdmerge.c
index dff5a3508..833ad6753 100644
--- a/jdmerge.c
+++ b/jdmerge.c
@@ -5,7 +5,7 @@
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
- * Copyright (C) 2009, 2011, 2014-2015, D. R. Commander.
+ * Copyright (C) 2009, 2011, 2014-2015, 2020, D. R. Commander.
  * Copyright (C) 2013, Linaro Limited.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
@@ -40,41 +40,13 @@
 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
+#include "jdmerge.h"
 #include "jsimd.h"
 #include "jconfigint.h"
 
 #ifdef UPSAMPLE_MERGING_SUPPORTED
 
 
-/* Private subobject */
-
-typedef struct {
-  struct jpeg_upsampler pub;    /* public fields */
-
-  /* Pointer to routine to do actual upsampling/conversion of one row group */
-  void (*upmethod) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
-                    JDIMENSION in_row_group_ctr, JSAMPARRAY output_buf);
-
-  /* Private state for YCC->RGB conversion */
-  int *Cr_r_tab;                /* => table for Cr to R conversion */
-  int *Cb_b_tab;                /* => table for Cb to B conversion */
-  JLONG *Cr_g_tab;              /* => table for Cr to G conversion */
-  JLONG *Cb_g_tab;              /* => table for Cb to G conversion */
-
-  /* For 2:1 vertical sampling, we produce two output rows at a time.
-   * We need a "spare" row buffer to hold the second output row if the
-   * application provides just a one-row buffer; we also use the spare
-   * to discard the dummy last row if the image height is odd.
-   */
-  JSAMPROW spare_row;
-  boolean spare_full;           /* T if spare buffer is occupied */
-
-  JDIMENSION out_row_width;     /* samples per output row */
-  JDIMENSION rows_to_go;        /* counts rows remaining in image */
-} my_upsampler;
-
-typedef my_upsampler *my_upsample_ptr;
-
 #define SCALEBITS       16      /* speediest right-shift on some machines */
 #define ONE_HALF        ((JLONG)1 << (SCALEBITS - 1))
 #define FIX(x)          ((JLONG)((x) * (1L << SCALEBITS) + 0.5))
@@ -189,7 +161,7 @@ typedef my_upsampler *my_upsample_ptr;
 LOCAL(void)
 build_ycc_rgb_table(j_decompress_ptr cinfo)
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
   int i;
   JLONG x;
   SHIFT_TEMPS
@@ -232,7 +204,7 @@ build_ycc_rgb_table(j_decompress_ptr cinfo)
 METHODDEF(void)
 start_pass_merged_upsample(j_decompress_ptr cinfo)
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
 
   /* Mark the spare buffer empty */
   upsample->spare_full = FALSE;
@@ -254,7 +226,7 @@ merged_2v_upsample(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                    JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
 /* 2:1 vertical sampling case: may need a spare row. */
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
   JSAMPROW work_ptrs[2];
   JDIMENSION num_rows;          /* number of rows returned to caller */
 
@@ -305,7 +277,7 @@ merged_1v_upsample(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                    JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
 /* 1:1 vertical sampling case: much easier, never need a spare row. */
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
 
   /* Just do the upsampling. */
   (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
@@ -566,11 +538,11 @@ h2v2_merged_upsample_565D(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
 GLOBAL(void)
 jinit_merged_upsampler(j_decompress_ptr cinfo)
 {
-  my_upsample_ptr upsample;
+  my_merged_upsample_ptr upsample;
 
-  upsample = (my_upsample_ptr)
+  upsample = (my_merged_upsample_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
-                                sizeof(my_upsampler));
+                                sizeof(my_merged_upsampler));
   cinfo->upsample = (struct jpeg_upsampler *)upsample;
   upsample->pub.start_pass = start_pass_merged_upsample;
   upsample->pub.need_context_rows = FALSE;
diff --git a/jdmerge.h b/jdmerge.h
new file mode 100644
index 000000000..b583396b1
--- /dev/null
+++ b/jdmerge.h
@@ -0,0 +1,47 @@
+/*
+ * jdmerge.h
+ *
+ * This file was part of the Independent JPEG Group's software:
+ * Copyright (C) 1994-1996, Thomas G. Lane.
+ * libjpeg-turbo Modifications:
+ * Copyright (C) 2020, D. R. Commander.
+ * For conditions of distribution and use, see the accompanying README.ijg
+ * file.
+ */
+
+#define JPEG_INTERNALS
+#include "jpeglib.h"
+
+#ifdef UPSAMPLE_MERGING_SUPPORTED
+
+
+/* Private subobject */
+
+typedef struct {
+  struct jpeg_upsampler pub;    /* public fields */
+
+  /* Pointer to routine to do actual upsampling/conversion of one row group */
+  void (*upmethod) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
+                    JDIMENSION in_row_group_ctr, JSAMPARRAY output_buf);
+
+  /* Private state for YCC->RGB conversion */
+  int *Cr_r_tab;                /* => table for Cr to R conversion */
+  int *Cb_b_tab;                /* => table for Cb to B conversion */
+  JLONG *Cr_g_tab;              /* => table for Cr to G conversion */
+  JLONG *Cb_g_tab;              /* => table for Cb to G conversion */
+
+  /* For 2:1 vertical sampling, we produce two output rows at a time.
+   * We need a "spare" row buffer to hold the second output row if the
+   * application provides just a one-row buffer; we also use the spare
+   * to discard the dummy last row if the image height is odd.
+   */
+  JSAMPROW spare_row;
+  boolean spare_full;           /* T if spare buffer is occupied */
+
+  JDIMENSION out_row_width;     /* samples per output row */
+  JDIMENSION rows_to_go;        /* counts rows remaining in image */
+} my_merged_upsampler;
+
+typedef my_merged_upsampler *my_merged_upsample_ptr;
+
+#endif /* UPSAMPLE_MERGING_SUPPORTED */
diff --git a/jdmrg565.c b/jdmrg565.c
index 1b87e3718..53f1e1670 100644
--- a/jdmrg565.c
+++ b/jdmrg565.c
@@ -5,7 +5,7 @@
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2013, Linaro Limited.
- * Copyright (C) 2014-2015, 2018, D. R. Commander.
+ * Copyright (C) 2014-2015, 2018, 2020, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -19,7 +19,7 @@ h2v1_merged_upsample_565_internal(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                                   JDIMENSION in_row_group_ctr,
                                   JSAMPARRAY output_buf)
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
   register int y, cred, cgreen, cblue;
   int cb, cr;
   register JSAMPROW outptr;
@@ -90,7 +90,7 @@ h2v1_merged_upsample_565D_internal(j_decompress_ptr cinfo,
                                    JDIMENSION in_row_group_ctr,
                                    JSAMPARRAY output_buf)
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
   register int y, cred, cgreen, cblue;
   int cb, cr;
   register JSAMPROW outptr;
@@ -163,7 +163,7 @@ h2v2_merged_upsample_565_internal(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                                   JDIMENSION in_row_group_ctr,
                                   JSAMPARRAY output_buf)
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
   register int y, cred, cgreen, cblue;
   int cb, cr;
   register JSAMPROW outptr0, outptr1;
@@ -259,7 +259,7 @@ h2v2_merged_upsample_565D_internal(j_decompress_ptr cinfo,
                                    JDIMENSION in_row_group_ctr,
                                    JSAMPARRAY output_buf)
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
   register int y, cred, cgreen, cblue;
   int cb, cr;
   register JSAMPROW outptr0, outptr1;
diff --git a/jdmrgext.c b/jdmrgext.c
index b1c27df56..c9a44d821 100644
--- a/jdmrgext.c
+++ b/jdmrgext.c
@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2011, 2015, D. R. Commander.
+ * Copyright (C) 2011, 2015, 2020, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -25,7 +25,7 @@ h2v1_merged_upsample_internal(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                               JDIMENSION in_row_group_ctr,
                               JSAMPARRAY output_buf)
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
   register int y, cred, cgreen, cblue;
   int cb, cr;
   register JSAMPROW outptr;
@@ -97,7 +97,7 @@ h2v2_merged_upsample_internal(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                               JDIMENSION in_row_group_ctr,
                               JSAMPARRAY output_buf)
 {
-  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
+  my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
   register int y, cred, cgreen, cblue;
   int cb, cr;
   register JSAMPROW outptr0, outptr1;
