bound shift width in dyncol integer readers

[jmestwa-coder]

Noticed the dyncol integer readers shift by an exponent taken from the value length. In dynamic_column_uint_read() the i*8 shift reaches 64 once a COLUMN_GET() blob gives an integer column more than 8 data bytes, and dynamic_column_var_uint_get() keeps shifting length*7 over a run of 0x80 continuation bytes (the charset id of a string value, intg/frac of a decimal). Both are undefined and abort under -fsanitize=shift. Reject the over-long integer and cap the varint at 10 groups.

[gemini-code-assist]

Code Review

This pull request introduces safety checks in mysys/ma_dyncol.c to prevent undefined behavior from bitwise shifts exceeding 64 bits. Specifically, it limits the loop in dynamic_column_var_uint_get to 10 iterations, rejects lengths greater than 8 in dynamic_column_uint_read, and ensures that dynamic_column_sint_read correctly propagates errors returned by dynamic_column_uint_read. No review comments were provided, and the changes appear correct.

[gkodinov]

Thank you for your contribution. This is a preliminary review!

This needs:

• a MDEV describing the problem, complete with steps to reproduce
• a commit message compliant with the MariaDB coding standards
• a regression test
• a rebase to the lowest affected version (this is a bug fix and not a feature).