From: "zhangyi (F)" <yi.zhang@huawei.com> hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4G4S5 --------------------------- files_fdtable() in files_cgroup_count_fds() should be invoked under files_struct->file_lock, otherwise a suspicious RCU usage warning triggers below when CONFIG_PROVE_RCU and CONFIG_LOCKDEP are enabled. ============================= WARNING: suspicious RCU usage ... ----------------------------- fs/filescontrol.c:96 suspicious rcu_dereference_check() usage! ... stack backtrace: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.36-cph920-32bitc-vmalloc-binder-debugon.aarch64 #6 Call trace: dump_backtrace+0x0/0x198 show_stack+0x24/0x30 dump_stack+0xd0/0x11c lockdep_rcu_suspicious+0xcc/0x110 files_cgroup_count_fds+0xc0/0xe0 dup_fd+0x234/0x448 copy_process.isra.2.part.3+0x698/0x1490 _do_fork+0xe8/0x728 kernel_thread+0x48/0x58 rest_init+0x34/0x2a0 start_kernel+0x52c/0x558 Although the 'newf' is newly created and will not be released in paralle, still silence the warning through adding spin_lock around. Fixes: 52cc1eccf6de ("cgroups: Resource controller for open files") Signed-off-by: zhangyi (F) <yi.zhang@huawei.com> Signed-off-by: chenridong <chenridong@huawei.com> --- fs/file.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/file.c b/fs/file.c index 6c63342ef506..a9558b693dba 100644 --- a/fs/file.c +++ b/fs/file.c @@ -408,8 +408,13 @@ struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int #ifdef CONFIG_CGROUP_FILES if (!files_cgroup_enabled()) return newf; - if (!files_cgroup_alloc_fd(newf, files_cgroup_count_fds(newf))) + spin_lock(&newf->file_lock); + if (!files_cgroup_alloc_fd(newf, files_cgroup_count_fds(newf))) { + spin_unlock(&newf->file_lock); return newf; + } + spin_unlock(&newf->file_lock); + /* could not get enough FD resources. Need to clean up. */ new_fds = new_fdt->fd; -- 2.34.1