The read stream callback apw_read_stream_next_block() advances p->pos
through the block_info array. When processing the last block, it
increments p->pos to prewarm_stop_idx before returning. The callback
itself is safe because it checks bounds before accessing the array.
However, the caller assigned blk from block_info[i] at the end of the
loop body, before the loop condition was re-evaluated. When i equaled
prewarm_stop_idx, this accessed memory beyond the allocated DSM segment,
causing a segfault.
Restructure the loop to check bounds at the top and assign blk at the
beginning of the loop body, where it is always safe. This avoids the
need for an explicit bounds check at the end.
Backpatch to 18, where the bug was introduced by commit 6acab8bdbc.
Author: Matheus Alcantara <mths.dev@pm.me>
Reported-by: Glauber Batista <glauberrbatista@gmail.com>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Tomas Vondra <tomas@vondra.me>
Backpatch-through: 18
Discussion: https://www.postgresql.org/message-id/CAO%2B_mTQgQyTYwDh%3DU8iTnsDmOGyWsZJjUV31SmEYwmw6_xY6Bw%40mail.gmail.com
The PostgreSQL contrib tree
---------------------------
This subtree contains porting tools, analysis utilities, and plug-in
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User documentation for each module appears in the main SGML
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When building from the source distribution, these modules are not
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Some directories supply new user-defined functions, operators, or
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CREATE EXTENSION module_name;
See the PostgreSQL documentation for more information about this
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