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Since741c10b096("kernfs: Use RCU to access kernfs_node::name.") a helper rdt_kn_name() that checks that rdtgroup_mutex is held has been used for all accesses to the kernfs node name. rdtgroup_mkdir() uses the name to determine if a valid monitor group is being created by checking the parent name is "mon_groups". This is done without holding rdtgroup_mutex, and now triggers the following warning: | WARNING: suspicious RCU usage | 6.15.0-rc1 #4465 Tainted: G E | ----------------------------- | arch/x86/kernel/cpu/resctrl/internal.h:408 suspicious rcu_dereference_check() usage! [...] | Call Trace: | <TASK> | dump_stack_lvl | lockdep_rcu_suspicious.cold | is_mon_groups | rdtgroup_mkdir | kernfs_iop_mkdir | vfs_mkdir | do_mkdirat | __x64_sys_mkdir | do_syscall_64 | entry_SYSCALL_64_after_hwframe Creating a control or monitor group calls mkdir_rdt_prepare(), which uses rdtgroup_kn_lock_live() to take the rdtgroup_mutex. To avoid taking and dropping the lock, move the check for the monitor group name and position into mkdir_rdt_prepare() so that it occurs under rdtgroup_mutex. Hoist is_mon_groups() earlier in the file. [ bp: Massage. ] Fixes:741c10b096("kernfs: Use RCU to access kernfs_node::name.") Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Acked-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20250407124637.2433230-1-james.morse@arm.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.