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Fri, 03 Apr 2026 06:30:43 -0700 (PDT) From: Weiming Shi To: Martin KaFai Lau , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi Cc: Song Liu , Yonghong Song , Jiri Olsa , Roman Gushchin , bpf@vger.kernel.org, Xiang Mei , Weiming Shi , Sun Jian , Paul Chaignon Subject: [PATCH bpf v2 1/2] bpf: fix end-of-list detection in cgroup_storage_get_next_key() Date: Fri, 3 Apr 2026 21:29:50 +0800 Message-ID: <20260403132951.43533-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260403132951.43533-1-bestswngs@gmail.com> References: <20260403132951.43533-1-bestswngs@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit list_next_entry() never returns NULL -- when the current element is the last entry it wraps to the list head via container_of(). The subsequent NULL check is therefore dead code and get_next_key() never returns -ENOENT for the last element, instead reading storage->key from a bogus pointer that aliases internal map fields and copying the result to userspace. Replace it with list_entry_is_head() so the function correctly returns -ENOENT when there are no more entries. Fixes: de9cbbaadba5 ("bpf: introduce cgroup storage maps") Reported-by: Xiang Mei Signed-off-by: Weiming Shi Reviewed-by: Sun Jian Acked-by: Paul Chaignon --- kernel/bpf/local_storage.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c index 8fca0c64f7b1c..23267213a17fb 100644 --- a/kernel/bpf/local_storage.c +++ b/kernel/bpf/local_storage.c @@ -270,7 +270,7 @@ static int cgroup_storage_get_next_key(struct bpf_map *_map, void *key, goto enoent; storage = list_next_entry(storage, list_map); - if (!storage) + if (list_entry_is_head(storage, &map->list, list_map)) goto enoent; } else { storage = list_first_entry(&map->list, -- 2.43.0