Skip privilege check in Information schema

[yiwen92]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

USE information_schema; 
CREATE user 'daily_dba'; 
GRANT Insert ON *.* TO 'daily_dba'@'%' WITH GRANT OPTION;

2. What did you expect to see? (Required)

exec good without error，just like mysql 8.0

3. What did you see instead (Required)

raise error: (8121, 'privilege check fail')

4. What is your TiDB version? (Required)

Release Version: v5.0.x and v4.0.x

[yiwen92]

this will affect version after 5.1.0, the root cause is no db info in processing process.

[tiancaiamao]

I checked master and master 6512fe5 is not affected

[tiancaiamao]

This is fixed by #23946, for the reason in #24142

It should be if dbName == "" && stmt.Level.Level != ast.GrantLevelGlobal {. There are also no tests on visitInfo for GrantLevelGlobal.

@morgo Would like to cherry-pick that fix to the old branch?

[morgo]

This is fixed by #23946, for the reason in #24142

It should be if dbName == "" && stmt.Level.Level != ast.GrantLevelGlobal {. There are also no tests on visitInfo for GrantLevelGlobal.

@morgo Would like to cherry-pick that fix to the old branch?

I chatted with @yiwen92 about it. It is not quite straight forward to cherry pick (it is based on other changes for dynamic privileges) but it should be easy enough to write a patch specific to 5.0.