[postgis-tickets] [PostGIS] #4017: lwgeom lexer memory corruption

[PostGIS]

#4017: lwgeom lexer memory corruption
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 Reporter:  petere     |      Owner:  strk
     Type:  defect     |     Status:  new
 Priority:  high       |  Milestone:  PostGIS 2.5.0
Component:  liblwgeom  |    Version:  trunk
 Keywords:             |
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 We have experienced frequent crashes in PostGIS, with backtraces pointing
 to memory corruption in the lwgeom lexer. I believe the attached patch
 fixes the problem. We have had it running for about a week without
 crashes, where before, they were quite frequent.

 The problem is that if a query is aborted while the lexer is running
 (e.g., statement timeout), the memory belonging to the internal lexer
 state is cleaned up by PostgreSQL, but the flex code thinks it's still
 there, so it will crash the next time the lexer runs. The fix is to
 reinitialize the flex globals before each run. (The same problem once
 existed in the core PostgreSQL code.)

 The problem was observed in version 2.2, but the same code exists in trunk
 as well. I suggest the fix could be backpatched.

 (You should regenerated the .c files using your preferred flex version.)

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4017>
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