On 11/10/23 8:38 PM, Hou Tao wrote:
From: Hou Tao <houtao1@xxxxxxxxxx>
bpf_mem_cache_alloc_flags() may call __alloc() directly when there is no
free object in free list, but it doesn't initialize the allocation hint
for the returned pointer. It may lead to bad memory dereference when
freeing the pointer, so fix it by initializing the allocation hint.
Fixes: 822fb26bdb55 ("bpf: Add a hint to allocated objects.")
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
LGTM based on my reading of the code. Maybe you could explain
how you found this issue and whether a test case can be constructed
relatively easily to expose this issue?
Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
kernel/bpf/memalloc.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
index 63b909d277d47..6a51cfe4c2d63 100644
--- a/kernel/bpf/memalloc.c
+++ b/kernel/bpf/memalloc.c
@@ -978,6 +978,8 @@ void notrace *bpf_mem_cache_alloc_flags(struct bpf_mem_alloc *ma, gfp_t flags)
memcg = get_memcg(c);
old_memcg = set_active_memcg(memcg);
ret = __alloc(c, NUMA_NO_NODE, GFP_KERNEL | __GFP_NOWARN | __GFP_ACCOUNT);
+ if (ret)
+ *(struct bpf_mem_cache **)ret = c;
set_active_memcg(old_memcg);
mem_cgroup_put(memcg);
}
