From 9b51a6155d14389876916726430da30eabb1d4ed Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Fri, 26 Jun 2026 17:52:52 +0200 Subject: [PATCH] bpf,fork: wipe ->bpf_storage before bailouts that access it Currently, copy_process() can bail out to free_task() before p->bpf_storage has been initialized, with this call graph (shown here for the !CONFIG_MEMCG case): copy_process dup_task_struct arch_dup_task_struct [copies the entire task_struct, including ->bpf_storage member] [RLIMIT_NPROC check fails] delayed_free_task free_task bpf_task_storage_free rcu_dereference(task->bpf_storage) bpf_local_storage_destroy In this case, the nascent task's ->bpf_storage member that bpf_local_storage_destroy() operates on is a plain copy of the parent's ->bpf_storage pointer, not a real initialized pointer. This leads to badness (kernel hangs, UAF). This is reachable as long as the process calling fork() has been inserted into a task storage map. Cc: stable@kernel.org Fixes: a10787e6d58c ("bpf: Enable task local storage for tracing programs") Signed-off-by: Jann Horn Signed-off-by: Andrii Nakryiko --- kernel/fork.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index 13e38e89a1f3..f0e2e131a9a5 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1009,6 +1009,11 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) tsk->mm_cid.active = 0; INIT_HLIST_NODE(&tsk->mm_cid.node); #endif + +#ifdef CONFIG_BPF_SYSCALL + RCU_INIT_POINTER(tsk->bpf_storage, NULL); + tsk->bpf_ctx = NULL; +#endif return tsk; free_stack: @@ -2247,10 +2252,6 @@ __latent_entropy struct task_struct *copy_process( p->sequential_io = 0; p->sequential_io_avg = 0; #endif -#ifdef CONFIG_BPF_SYSCALL - RCU_INIT_POINTER(p->bpf_storage, NULL); - p->bpf_ctx = NULL; -#endif unwind_task_init(p); -- 2.47.3