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Fix buffer zeroing with offset in map_buffer #2916

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merged 4 commits into from
Jul 31, 2022

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nical
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@nical nical commented Jul 26, 2022

Checklist

  • Run cargo clippy.
  • Add change to CHANGELOG.md. See simple instructions inside file.

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Description

The buffer zeroing code in map_buffer currently writes out of bounds if a non zero offset is passed.

This is because the map_buffer code passes the mapped_pointer + uninitialized.start to write_bytes, however the uninitialized range is relative to the start of the buffer while our mapped pointer is offset.

The offset parameter has to be subtracted from the uninitialized range so that the new range is relative to the mapped range and avoid (very scary) out of bounds writes.

Testing

None.

The tracked uninitialized ranges are relative to the start of the buffer, however when mapping the buffer at an offset the resulting pointer is not the start of the buffer, and therefore the offset has to be taken into account.
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@jimblandy jimblandy left a comment

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Wow.

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@cwfitzgerald cwfitzgerald left a comment

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Very nice stuff

@cwfitzgerald cwfitzgerald enabled auto-merge (squash) July 31, 2022 21:54
@cwfitzgerald cwfitzgerald merged commit a05c8dc into gfx-rs:master Jul 31, 2022
@nical nical deleted the map_clear_offset branch July 31, 2022 23:01
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3 participants