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Huff decs: Fix/suppress more innocuous UBSan errs

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- UBSan complained that entropy->restarts_to_go was underflowing an
  unsigned integer when it was decremented while
  cinfo->restart_interval == 0.  That was, of course, completely
  innocuous behavior, since the result of the underflowing computation
  was never used.

- d3a3a73f64 and
  7bc9fca430 silenced a UBSan signed
  integer overflow error, but unfortunately other malformed JPEG images
  have been discovered that cause unsigned integer overflow in the same
  computation.  Since, to the best of our understanding, this behavior
  is innocuous, this commit reverts the commits listed above, suppresses
  the UBSan errors, and adds code comments to document the issue.
This commit is contained in:
DRC
2021-04-15 23:31:51 -05:00
parent 8fa70367ed
commit d147be83e9
2 changed files with 26 additions and 11 deletions
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14
jdphuff.c
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@@ -4,7 +4,7 @@
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1995-1997, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2015-2016, 2018-2020, D. R. Commander.
* Copyright (C) 2015-2016, 2018-2021, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
@@ -348,7 +348,8 @@ decode_mcu_DC_first(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
}
/* Account for restart interval (no-op if not using restarts) */
entropy->restarts_to_go--;
if (cinfo->restart_interval)
entropy->restarts_to_go--;
return TRUE;
}
@@ -432,7 +433,8 @@ decode_mcu_AC_first(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
}
/* Account for restart interval (no-op if not using restarts) */
entropy->restarts_to_go--;
if (cinfo->restart_interval)
entropy->restarts_to_go--;
return TRUE;
}
@@ -483,7 +485,8 @@ decode_mcu_DC_refine(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
/* Account for restart interval (no-op if not using restarts) */
entropy->restarts_to_go--;
if (cinfo->restart_interval)
entropy->restarts_to_go--;
return TRUE;
}
@@ -626,7 +629,8 @@ decode_mcu_AC_refine(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
}
/* Account for restart interval (no-op if not using restarts) */
entropy->restarts_to_go--;
if (cinfo->restart_interval)
entropy->restarts_to_go--;
return TRUE;