MySQL Bugs: #108947: mysql-8.0.31: build fails if building user cannot access mysqld's tempdir

Bug #108947	mysql-8.0.31: build fails if building user cannot access mysqld's tempdir
Submitted:	1 Nov 2022 4:40	Modified:	21 Nov 2022 18:02
Reporter:	Hank Leininger	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Compiling	Severity:	S3 (Non-critical)
Version:	8.0.31	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	BuildID, CREATE_INFO_BIN

Description:
If a host has mysql configured to use a tmpdir that only the mysql user can access, and mysql is compiled as a different user, the build will fail towards the very end; in the below example on Gentoo Linux, mysql is compiled by user portage under a /var/tmp/portage/... path:

[100%] Generating Docs/INFO_BIN
/usr/bin/cmake -DMYSQLD_EXECUTABLE=/var/tmp/portage/dev-db/mysql-8.0.31/work/mysql_build/runtime_output_directory/mysqld -DCMAKE_BUILD_TYPE=RelWithDebInfo -P /var/tmp/portage/dev-db/mysql-8.0.31/work/mysql/cmake/info_bin.cmake
CMake Error at info_macros.cmake:185 (MESSAGE):
  mysqld --help failed: mysqld: Can't get stat of '/usr/local/mysql-data/tmp'
  (OS errno 13 - Permission denied)

  2022-11-01T03:14:41.014206Z 0 [ERROR] [MY-010119] [Server] Aborting

Call Stack (most recent call first):
  /var/tmp/portage/dev-db/mysql-8.0.31/work/mysql/cmake/info_bin.cmake:36 (CREATE_INFO_BIN)

make[2]: *** [CMakeFiles/INFO_BIN.dir/build.make:71: CMakeFiles/INFO_BIN] Error 1
make[2]: Leaving directory '/var/tmp/portage/dev-db/mysql-8.0.31/work/mysql_build'
make[1]: *** [CMakeFiles/Makefile2:2735: CMakeFiles/INFO_BIN.dir/all] Error 2
make[1]: Leaving directory '/var/tmp/portage/dev-db/mysql-8.0.31/work/mysql_build'
make: *** [Makefile:156: all] Error 2

Here info_bin.cmake is calling CREATE_INFO_BIN defined in cmake/info_macros.cmake.in

In my case, mysql's tmpdir = /usr/local/mysql-data/tmp, which is mysql-only, inaccessible to user portage:

# namei -l /usr/local/mysql-data/tmp
f: /usr/local/mysql-data/tmp
drwxr-xr-x root  root  /
drwxr-xr-x root  root  usr
drwxr-xr-x root  root  local
drwxrwx--T root  mysql mysql-data
drwxr-xr-x mysql mysql tmp

How to repeat:
1) Create a path that is only accessible to user mysql

2) configure /etc/mysql/... to set tmpdir= to some path under #1

3) Compile mysql as a non-root, non-mysql user

4) When build is nearly complete, it aborts with the above error.

Suggested fix:
This was never a problem until recently; sometime between 8.0.27 and 8.0.31 this was added:

$ diff -u \
  mysql-8.0.27/work/mysql/cmake/info_macros.cmake.in \
  mysql-8.0.31/work/mysql/cmake/info_macros.cmake.in
...
+  IF(HAVE_BUILD_ID_SUPPORT AND NOT WITHOUT_SERVER)
+    FILE(APPEND ${INFO_BIN} "\n===== BUILD ID =====\n")
+    EXECUTE_PROCESS(COMMAND
+      ${MYSQLD_EXECUTABLE} --help
+      OUTPUT_VARIABLE mysqld_help
...

This will call the just-built mysqld binary, but it reads in configs from the real /etc/mysql/ if present, causing an error.

So the fix is to avoid reading the system's in-place configs, if any.

Adding --no-defaults to that mysqld invocation avoids the problem of the build user trying to follow paths only user mysql can access, but still includes the BuildID in the output that the recipe wants. So:

--- a/cmake/info_macros.cmake.in        2022-09-13 12:15:16.000000000 -0400
+++ b/cmake/info_macros.cmake.in        2022-11-01 00:12:06.270464679 -0400
@@ -175,7 +175,7 @@
   IF(HAVE_BUILD_ID_SUPPORT AND NOT WITHOUT_SERVER)
     FILE(APPEND ${INFO_BIN} "\n===== BUILD ID =====\n")
     EXECUTE_PROCESS(COMMAND
-      ${MYSQLD_EXECUTABLE} --help
+      ${MYSQLD_EXECUTABLE} --no-defaults --help
       OUTPUT_VARIABLE mysqld_help
       RESULT_VARIABLE mysqld_help_result
       ERROR_VARIABLE mysqld_help_error

Hi Mr. Leininger,

Thank you for your bug report.

However, Gentoo is not among the supported Linux platforms, which you can notice yourself on our Download pages.

Regarding `tmpdir`, we require that user building from the source has all privileges on that directory. We shall check whether we have to add that to our Reference Manual.

Unsupported.

Gentoo is not particularly relevant here, the important thing is the currently-building mysqld should not load any system-installed conf files; it should load none, or, load only the currently-building default files.

You do not see how it can be a problem that during compilation, existing/production configs are loaded?

Hi!

Thanks for your report, indeed adding --no-defaults was forgotten when adding this code to run the newly built mysqld.

The common pattern of adding --no-defaults is used several places in the test suite to avoid exactly such problems.

Posted by developer:
 
Fixed as of the upcoming MySQL Server 8.0.32 release, and here's the proposed changelog entry from the documentation team:

Building MySQL would fail if the building user lacked access to mysqld's
temporary directory. Now --no-defaults is used when creating the INFO_BIN
file.

Thank you for the bug report.

Thank you, Philip.