netdev - [PATCH bpf-next v4 09/16] bpf: Prepare for bpf_selem_unlink

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260131050920.2574084-10-ameryhung@gmail.com>
Date: Fri, 30 Jan 2026 21:09:12 -0800
From: Amery Hung <ameryhung@...il.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
	alexei.starovoitov@...il.com,
	andrii@...nel.org,
	daniel@...earbox.net,
	memxor@...il.com,
	martin.lau@...nel.org,
	kpsingh@...nel.org,
	yonghong.song@...ux.dev,
	song@...nel.org,
	haoluo@...gle.com,
	ameryhung@...il.com,
	kernel-team@...a.com
Subject: [PATCH bpf-next v4 09/16] bpf: Prepare for bpf_selem_unlink_nofail()

The next patch will introduce bpf_selem_unlink_nofail() to handle
rqspinlock errors. bpf_selem_unlink_nofail() will allow an selem to be
partially unlinked from map or local storage. Save memory allocation
method in selem so that later an selem can be correctly freed even when
SDATA(selem)->smap is init to NULL.

In addition, keep track of memory charge to the owner in local storage
so that later bpf_selem_unlink_nofail() can return the correct memory
charge to the owner. Updating selems_size is protected by
local_storage->lock.

Signed-off-by: Amery Hung <ameryhung@...il.com>
---
 include/linux/bpf_local_storage.h |  4 +++-
 kernel/bpf/bpf_local_storage.c    | 10 +++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h
index 70b35dfc01c9..ece32f756d86 100644
--- a/include/linux/bpf_local_storage.h
+++ b/include/linux/bpf_local_storage.h
@@ -80,7 +80,8 @@ struct bpf_local_storage_elem {
 						 * after raw_spin_unlock
 						 */
 	};
-	/* 8 bytes hole */
+	bool use_kmalloc_nolock;
+	/* 7 bytes hole */
 	/* The data is stored in another cacheline to minimize
 	 * the number of cachelines access during a cache hit.
 	 */
@@ -96,6 +97,7 @@ struct bpf_local_storage {
 				 */
 	struct rcu_head rcu;
 	rqspinlock_t lock;	/* Protect adding/removing from the "list" */
+	u64 selems_size;	/* Total selem size. Protected by "lock" */
 	bool use_kmalloc_nolock;
 };
 
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index fbf41e00be8a..b8f146d41ffe 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -85,6 +85,7 @@ bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner,
 
 	if (selem) {
 		RCU_INIT_POINTER(SDATA(selem)->smap, smap);
+		selem->use_kmalloc_nolock = smap->use_kmalloc_nolock;
 
 		if (value) {
 			/* No need to call check_and_init_map_value as memory is zero init */
@@ -214,7 +215,7 @@ void bpf_selem_free(struct bpf_local_storage_elem *selem,
 
 	smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
 
-	if (!smap->use_kmalloc_nolock) {
+	if (!selem->use_kmalloc_nolock) {
 		/*
 		 * No uptr will be unpin even when reuse_now == false since uptr
 		 * is only supported in task local storage, where
@@ -305,12 +306,19 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
 	if (rcu_access_pointer(local_storage->smap) == smap)
 		RCU_INIT_POINTER(local_storage->smap, NULL);
 
+	local_storage->selems_size -= smap->elem_size;
+
 	return free_local_storage;
 }
 
 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
 				   struct bpf_local_storage_elem *selem)
 {
+	struct bpf_local_storage_map *smap;
+
+	smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
+	local_storage->selems_size += smap->elem_size;
+
 	RCU_INIT_POINTER(selem->local_storage, local_storage);
 	hlist_add_head_rcu(&selem->snode, &local_storage->list);
 }
-- 
2.47.3