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charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 9DBEF4000E X-Stat-Signature: 1xxz9x36s84npj15anzi6ip3e5xzfz86 X-Rspam-User: X-HE-Tag: 1772193838-40368 X-HE-Meta: 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 FdztL1vT cUizkeu4XbKlY9E87Bf/d+XGI2ZWE56la16jxycWOo0u7vIdOinwG4cS5T3vb1gXjavkNcMRU3jWuYAQiJTwM+87dida8ir+5jYCdce4T5b2SNSE/Ey/MMFxapqYH+exPo4DExaE3EzzFLMpJxOTXLRy47rxadcv3Oa8wGS4I3JaWHE1qysvkGz0vncNk3+wN7z8V9DzumoFycMKVp5MrXOQybVXgrnKAnsVoJUGculuwYOIAOvCJApUBiN/1Zy6gV4Ga6oob3cVJsoxTOR5Z/4F3skOOYEmdtJSi0uZoWlB1pCa/sSko0U3VnOoAYjscoEGDNbVdsMhqgN7vUZAqS5SQgx50fXqTcMlRP8WSuPOjiU6KJYGaVJVqFEt7EzcrYGcP1rJV/DWY/OluJQzCqHYXe6nlV0nFJiZfbMAa8cekAiY+M+hF7PqU0KWQDDlDjbBZNX3EbVvlE94= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Currently we allow only one attempt to create init in a new namespace. If the first fork() fails after alloc_pid() succeeds, free_pid() clears PIDNS_ADDING and thus disables further PID allocations. Nowadays this looks like an unnecessary limitation. The original reason to handle "case PIDNS_ADDING" in free_pid() is gone, most probably after commit 69879c01a0c3 ("proc: Remove the now unnecessary internal mount of proc"). Change free_pid() to keep ns->pid_allocated == PIDNS_ADDING, and change alloc_pid() to reset the cursor early, right after taking pidmap_lock. Test-case: #define _GNU_SOURCE #include #include #include #include #include #include int main(void) { struct clone_args args = { .exit_signal = SIGCHLD, .flags = CLONE_PIDFD, .pidfd = 0, }; unsigned long pidfd; int pid; assert(unshare(CLONE_NEWPID) == 0); pid = syscall(__NR_clone3, &args, sizeof(args)); assert(pid == -1 && errno == EFAULT); args.pidfd = (unsigned long)&pidfd; pid = syscall(__NR_clone3, &args, sizeof(args)); if (pid) assert(pid > 0 && wait(NULL) == pid); else assert(getpid() == 1); return 0; } Signed-off-by: Oleg Nesterov --- kernel/pid.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/kernel/pid.c b/kernel/pid.c index ebf013f35cb3..1a0d2ac1f4a9 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -131,9 +131,8 @@ void free_pid(struct pid *pid) wake_up_process(ns->child_reaper); break; case PIDNS_ADDING: - /* Handle a fork failure of the first process */ - WARN_ON(ns->child_reaper); - ns->pid_allocated = 0; + /* Only possible if the 1st fork fails */ + WARN_ON(READ_ONCE(ns->child_reaper)); break; } @@ -230,6 +229,10 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *arg_set_tid, retried_preload = false; idr_preload(GFP_KERNEL); spin_lock(&pidmap_lock); + /* For the case when the previous attempt to create init failed */ + if (ns->pid_allocated == PIDNS_ADDING) + idr_set_cursor(&ns->idr, 0); + for (tmp = ns, i = ns->level; i >= 0;) { int tid = set_tid[ns->level - i]; @@ -341,10 +344,6 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *arg_set_tid, idr_remove(&upid->ns->idr, upid->nr); } - /* On failure to allocate the first pid, reset the state */ - if (ns->pid_allocated == PIDNS_ADDING) - idr_set_cursor(&ns->idr, 0); - spin_unlock(&pidmap_lock); idr_preload_end(); -- 2.52.0