Petr Pavlu 0254127ab9 module: Don't wait for GOING modules ... During a system boot, it can happen that the kernel receives a burst of requests to insert the same module but loading it eventually fails during its init call. For instance, udev can make a request to insert a frequency module for each individual CPU when another frequency module is already loaded which causes the init function of the new module to return an error. Since commit 6e6de3dee5 ("kernel/module.c: Only return -EEXIST for modules that have finished loading"), the kernel waits for modules in MODULE_STATE_GOING state to finish unloading before making another attempt to load the same module. This creates unnecessary work in the described scenario and delays the boot. In the worst case, it can prevent udev from loading drivers for other devices and might cause timeouts of services waiting on them and subsequently a failed boot. This patch attempts a different solution for the problem 6e6de3dee5 was trying to solve. Rather than waiting for the unloading to complete, it returns a different error code (-EBUSY) for modules in the GOING state. This should avoid the error situation that was described in 6e6de3dee5 (user space attempting to load a dependent module because the -EEXIST error code would suggest to user space that the first module had been loaded successfully), while avoiding the delay situation too. This has been tested on linux-next since December 2022 and passes all kmod selftests except test 0009 with module compression enabled but it has been confirmed that this issue has existed and has gone unnoticed since prior to this commit and can also be reproduced without module compression with a simple usleep(5000000) on tools/modprobe.c [0]. These failures are caused by hitting the kernel mod_concurrent_max and can happen either due to a self inflicted kernel module auto-loead DoS somehow or on a system with large CPU count and each CPU count incorrectly triggering many module auto-loads. Both of those issues need to be fixed in-kernel. [0] https://lore.kernel.org/all/Y9A4fiobL6IHp%2F%2FP@bombadil.infradead.org/ Fixes: 6e6de3dee5 ("kernel/module.c: Only return -EEXIST for modules that have finished loading") Co-developed-by: Martin Wilck <mwilck@suse.com> Signed-off-by: Martin Wilck <mwilck@suse.com> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> Cc: stable@vger.kernel.org Reviewed-by: Petr Mladek <pmladek@suse.com> [mcgrof: enhance commit log with testing and kmod test result interpretation ] Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>		2023-01-24 12:52:52 -08:00
..
debug_kmemleak.c
decompress.c	module/decompress: Support zstd in-kernel decompression	2022-12-07 12:05:05 -08:00
internal.h	dyndbg: gather __dyndbg[] state into struct _ddebug_info	2022-09-07 17:04:48 +02:00
kallsyms.c	kallsyms: Make module_kallsyms_on_each_symbol generally available	2022-10-25 10:14:50 -07:00
Kconfig	module/decompress: Support zstd in-kernel decompression	2022-12-07 12:05:05 -08:00
kdb.c
livepatch.c
main.c	module: Don't wait for GOING modules	2023-01-24 12:52:52 -08:00
Makefile
procfs.c	module: Modify module_flags() to accept show_state argument	2022-07-14 17:40:23 -07:00
signing.c
strict_rwx.c
sysfs.c	module: remove redundant module_sysfs_initialized variable	2022-11-11 10:19:52 -08:00
tracking.c	module: tracking: Keep a record of tainted unloaded modules only	2022-10-10 12:16:19 -07:00
tree_lookup.c
version.c