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[sfnt] Fix crash in `Load_SBit_Png` on Windows x64. 

This change fixes a crash that occurs in `Load_SBit_Png` when
running on a 64-bit Windows OS.  A memory access violation exception
would be raised by `setjmp` if the `jmp_buf` is not aligned to a
16-byte memory boundary.  This is due to setjmp executing `movdqa`
instructions to store 128-bit XMM registers to memory, which require
correct memory alignment.  This problem occurs because
`png_create_read_struct` uses `malloc` and `free` for memory
management, which only guarantees 8-byte alignment on Windows.

Instead, to fix the problem, `png_create_read_struct_2` is used on
64-bit Windows, which allows for user-defined memory allocation and
deallocation callbacks to be specified.  These callbacks forward the
allocation and deallocation requests to `_aligned_alloc` and
`_aligned_free`, ensuring that the allocated `png_struct` and
internal `jmp_buf` have the requisite 16-byte alignment.

* src/sfnt/pngshim.c <_WIN64>: Include `malloc.h`.
(malloc_callback, free_callback) <_WIN64>: New functions.
(Load_SBit_Png) <_WIN64>: Use `png_create_read_struct_2` instead of
`png_create_read_struct`
This commit is contained in:
Jesse Towner 2021-02-25 15:07:25 -08:00 committed by Werner Lemberg
parent f7d7e7f9f7
commit dbf9142f7e
2 changed files with 71 additions and 0 deletions
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25
ChangeLog
View File

@ -1,3 +1,28 @@
2021-02-27 Jesse Towner <townerj@gmail.com>
[sfnt] Fix crash in `Load_SBit_Png` on Windows x64.
This change fixes a crash that occurs in `Load_SBit_Png` when
running on a 64-bit Windows OS. A memory access violation exception
would be raised by `setjmp` if the `jmp_buf` is not aligned to a
16-byte memory boundary. This is due to setjmp executing `movdqa`
instructions to store 128-bit XMM registers to memory, which require
correct memory alignment. This problem occurs because
`png_create_read_struct` uses `malloc` and `free` for memory
management, which only guarantees 8-byte alignment on Windows.
Instead, to fix the problem, `png_create_read_struct_2` is used on
64-bit Windows, which allows for user-defined memory allocation and
deallocation callbacks to be specified. These callbacks forward the
allocation and deallocation requests to `_aligned_alloc` and
`_aligned_free`, ensuring that the allocated `png_struct` and
internal `jmp_buf` have the requisite 16-byte alignment.
* src/sfnt/pngshim.c <_WIN64>: Include `malloc.h`.
(malloc_callback, free_callback) <_WIN64>: New functions.
(Load_SBit_Png) <_WIN64>: Use `png_create_read_struct_2` instead of
`png_create_read_struct`
2021-02-25 Werner Lemberg <wl@gnu.org>
[woff2] Fix memory leak.

46
src/sfnt/pngshim.c
View File

@ -33,6 +33,16 @@
#include "sferrors.h"
/* Use _aligned_malloc / _aligned_free on 64-bit Windows to ensure that */
/* the jmp_buf needed for ft_setjmp is aligned to a 16-byte boundary. */
/* If the jmp_buf is not aligned to a 16-byte boundary then a memory */
/* access violation exception will occur upon ft_setjmp being called. */
#ifdef _WIN64
#ifndef PNG_USER_MEM_SUPPORTED
#error "libpng user-defined memory allocation is required for 64-bit Windows"
#endif
#include <malloc.h>
#endif
/* This code is freely based on cairo-png.c. There's so many ways */
/* to call libpng, and the way cairo does it is defacto standard. */
@ -221,6 +231,32 @@
}
#ifdef _WIN64
/* Memory allocation callback to ensure that the jmp_buf that is stored */
/* within the png_struct has 16-byte alignment for 64-bit Windows. */
static png_voidp
malloc_callback( png_structp png,
png_alloc_size_t size )
{
FT_UNUSED( png );
return _aligned_malloc( size, 16 );
}
/* Memory deallocation callback to release memory that was allocated */
/* with the matching memory allocation callback above. */
static void
free_callback( png_structp png,
png_voidp ptr )
{
FT_UNUSED( png );
_aligned_free( ptr );
}
#endif /* _WIN64 */
static void
read_data_from_FT_Stream( png_structp png,
png_bytep data,
@ -292,10 +328,20 @@
FT_Stream_OpenMemory( &stream, data, png_len );
#ifdef _WIN64
png = png_create_read_struct_2( PNG_LIBPNG_VER_STRING,
&error,
error_callback,
warning_callback,
NULL,
malloc_callback,
free_callback );
#else
png = png_create_read_struct( PNG_LIBPNG_VER_STRING,
&error,
error_callback,
warning_callback );
#endif
if ( !png )
{
error = FT_THROW( Out_Of_Memory );