This is a note to let you know that I've just added the patch titled bpf: Fix usage of trace RCU in local storage. to the 5.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bpf-fix-usage-of-trace-rcu-in-local-storage.patch and it can be found in the queue-5.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From dcf456c9a095a6e71f53d6f6f004133ee851ee70 Mon Sep 17 00:00:00 2001 From: KP Singh <kpsingh@xxxxxxxxxx> Date: Mon, 18 Apr 2022 15:51:58 +0000 Subject: bpf: Fix usage of trace RCU in local storage. From: KP Singh <kpsingh@xxxxxxxxxx> commit dcf456c9a095a6e71f53d6f6f004133ee851ee70 upstream. bpf_{sk,task,inode}_storage_free() do not need to use call_rcu_tasks_trace as no BPF program should be accessing the owner as it's being destroyed. The only other reader at this point is bpf_local_storage_map_free() which uses normal RCU. The only path that needs trace RCU are: * bpf_local_storage_{delete,update} helpers * map_{delete,update}_elem() syscalls Fixes: 0fe4b381a59e ("bpf: Allow bpf_local_storage to be used by sleepable programs") Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Acked-by: Martin KaFai Lau <kafai@xxxxxx> Link: https://lore.kernel.org/bpf/20220418155158.2865678-1-kpsingh@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/bpf_local_storage.h | 4 ++-- kernel/bpf/bpf_inode_storage.c | 4 ++-- kernel/bpf/bpf_local_storage.c | 29 +++++++++++++++++++---------- kernel/bpf/bpf_task_storage.c | 4 ++-- net/core/bpf_sk_storage.c | 6 +++--- 5 files changed, 28 insertions(+), 19 deletions(-) --- a/include/linux/bpf_local_storage.h +++ b/include/linux/bpf_local_storage.h @@ -143,9 +143,9 @@ void bpf_selem_link_storage_nolock(struc bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage, struct bpf_local_storage_elem *selem, - bool uncharge_omem); + bool uncharge_omem, bool use_trace_rcu); -void bpf_selem_unlink(struct bpf_local_storage_elem *selem); +void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu); void bpf_selem_link_map(struct bpf_local_storage_map *smap, struct bpf_local_storage_elem *selem); --- a/kernel/bpf/bpf_inode_storage.c +++ b/kernel/bpf/bpf_inode_storage.c @@ -90,7 +90,7 @@ void bpf_inode_storage_free(struct inode */ bpf_selem_unlink_map(selem); free_inode_storage = bpf_selem_unlink_storage_nolock( - local_storage, selem, false); + local_storage, selem, false, false); } raw_spin_unlock_bh(&local_storage->lock); rcu_read_unlock(); @@ -149,7 +149,7 @@ static int inode_storage_delete(struct i if (!sdata) return -ENOENT; - bpf_selem_unlink(SELEM(sdata)); + bpf_selem_unlink(SELEM(sdata), true); return 0; } --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -106,7 +106,7 @@ static void bpf_selem_free_rcu(struct rc */ bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage, struct bpf_local_storage_elem *selem, - bool uncharge_mem) + bool uncharge_mem, bool use_trace_rcu) { struct bpf_local_storage_map *smap; bool free_local_storage; @@ -150,11 +150,16 @@ bool bpf_selem_unlink_storage_nolock(str SDATA(selem)) RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL); - call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu); + if (use_trace_rcu) + call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu); + else + kfree_rcu(selem, rcu); + return free_local_storage; } -static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem) +static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem, + bool use_trace_rcu) { struct bpf_local_storage *local_storage; bool free_local_storage = false; @@ -169,12 +174,16 @@ static void __bpf_selem_unlink_storage(s raw_spin_lock_irqsave(&local_storage->lock, flags); if (likely(selem_linked_to_storage(selem))) free_local_storage = bpf_selem_unlink_storage_nolock( - local_storage, selem, true); + local_storage, selem, true, use_trace_rcu); raw_spin_unlock_irqrestore(&local_storage->lock, flags); - if (free_local_storage) - call_rcu_tasks_trace(&local_storage->rcu, + if (free_local_storage) { + if (use_trace_rcu) + call_rcu_tasks_trace(&local_storage->rcu, bpf_local_storage_free_rcu); + else + kfree_rcu(local_storage, rcu); + } } void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, @@ -214,14 +223,14 @@ void bpf_selem_link_map(struct bpf_local raw_spin_unlock_irqrestore(&b->lock, flags); } -void bpf_selem_unlink(struct bpf_local_storage_elem *selem) +void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu) { /* Always unlink from map before unlinking from local_storage * because selem will be freed after successfully unlinked from * the local_storage. */ bpf_selem_unlink_map(selem); - __bpf_selem_unlink_storage(selem); + __bpf_selem_unlink_storage(selem, use_trace_rcu); } struct bpf_local_storage_data * @@ -466,7 +475,7 @@ bpf_local_storage_update(void *owner, st if (old_sdata) { bpf_selem_unlink_map(SELEM(old_sdata)); bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata), - false); + false, true); } unlock: @@ -548,7 +557,7 @@ void bpf_local_storage_map_free(struct b migrate_disable(); __this_cpu_inc(*busy_counter); } - bpf_selem_unlink(selem); + bpf_selem_unlink(selem, false); if (busy_counter) { __this_cpu_dec(*busy_counter); migrate_enable(); --- a/kernel/bpf/bpf_task_storage.c +++ b/kernel/bpf/bpf_task_storage.c @@ -102,7 +102,7 @@ void bpf_task_storage_free(struct task_s */ bpf_selem_unlink_map(selem); free_task_storage = bpf_selem_unlink_storage_nolock( - local_storage, selem, false); + local_storage, selem, false, false); } raw_spin_unlock_irqrestore(&local_storage->lock, flags); bpf_task_storage_unlock(); @@ -192,7 +192,7 @@ static int task_storage_delete(struct ta if (!sdata) return -ENOENT; - bpf_selem_unlink(SELEM(sdata)); + bpf_selem_unlink(SELEM(sdata), true); return 0; } --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -40,7 +40,7 @@ static int bpf_sk_storage_del(struct soc if (!sdata) return -ENOENT; - bpf_selem_unlink(SELEM(sdata)); + bpf_selem_unlink(SELEM(sdata), true); return 0; } @@ -75,8 +75,8 @@ void bpf_sk_storage_free(struct sock *sk * sk_storage. */ bpf_selem_unlink_map(selem); - free_sk_storage = bpf_selem_unlink_storage_nolock(sk_storage, - selem, true); + free_sk_storage = bpf_selem_unlink_storage_nolock( + sk_storage, selem, true, false); } raw_spin_unlock_bh(&sk_storage->lock); rcu_read_unlock(); Patches currently in stable-queue which might be from kpsingh@xxxxxxxxxx are queue-5.18/bpf-fix-usage-of-trace-rcu-in-local-storage.patch