bpo-31626: Fix _PyMem_DebugRawRealloc() on OpenBSD #4119
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Fix memory debug hooks on OpenBSD: fix _PyMem_DebugRawRealloc(). Previously, the old resized memory block was modified after realloc() success to fill now unused bytes with the DEADBYTE pattern. On OpenBSD, modifying the old memory block causes a fatal error. On OpenBSD, the function now erases the bytes *before* calling realloc(), but keep a copy of erased bytes to restore them if realloc() fails. The behaviour on other platforms is unchanged: erased bytes *after* realloc() success. Co-Authored-By: Serhiy Storchaka <storchaka@gmail.com>
vstinner
commented
Oct 25, 2017
| memory block on realloc() success: the program is killed by a fatal | ||
| trap signal. So erase bytes before, but keep a copy to restore erased | ||
| bytes if realloc() fails. */ | ||
| # define REALLOC_WRITE_BEFORE |
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Maybe it would be simpler to modify _PyMem_DebugRawRealloc() to behave "correctly" on all platforms. What do you think?
I don't think that the "copy" memory allocation is a real blocker issue. It's a debug hook, I consider that the memory usage is not a big deal here.
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@serhiy-storchaka merged a simpler fix: PR #3844. |
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Fix memory debug hooks on OpenBSD: fix _PyMem_DebugRawRealloc().
Previously, the old resized memory block was modified after realloc()
success to fill now unused bytes with the DEADBYTE pattern. On
OpenBSD, modifying the old memory block causes a fatal error.
On OpenBSD, the function now erases the bytes before calling
realloc(), but keep a copy of erased bytes to restore them if
realloc() fails.
The behaviour on other platforms is unchanged: erased bytes after
realloc() success.
Co-Authored-By: Serhiy Storchaka storchaka@gmail.com
https://bugs.python.org/issue31626