From 5fb750e8a9ae123b2034771b864b8a21dbef65cd Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Tue, 14 Oct 2025 17:07:00 -0700 Subject: bpf: Replace bpf_map_kmalloc_node() with kmalloc_nolock() to allocate bpf_async_cb structures. The following kmemleak splat: [ 8.105530] kmemleak: Trying to color unknown object at 0xff11000100e918c0 as Black [ 8.106521] Call Trace: [ 8.106521] [ 8.106521] dump_stack_lvl+0x4b/0x70 [ 8.106521] kvfree_call_rcu+0xcb/0x3b0 [ 8.106521] ? hrtimer_cancel+0x21/0x40 [ 8.106521] bpf_obj_free_fields+0x193/0x200 [ 8.106521] htab_map_update_elem+0x29c/0x410 [ 8.106521] bpf_prog_cfc8cd0f42c04044_overwrite_cb+0x47/0x4b [ 8.106521] bpf_prog_8c30cd7c4db2e963_overwrite_timer+0x65/0x86 [ 8.106521] bpf_prog_test_run_syscall+0xe1/0x2a0 happens due to the combination of features and fixes, but mainly due to commit 6d78b4473cdb ("bpf: Tell memcg to use allow_spinning=false path in bpf_timer_init()") It's using __GFP_HIGH, which instructs slub/kmemleak internals to skip kmemleak_alloc_recursive() on allocation, so subsequent kfree_rcu()-> kvfree_call_rcu()->kmemleak_ignore() complains with the above splat. To fix this imbalance, replace bpf_map_kmalloc_node() with kmalloc_nolock() and kfree_rcu() with call_rcu() + kfree_nolock() to make sure that the objects allocated with kmalloc_nolock() are freed with kfree_nolock() rather than the implicit kfree() that kfree_rcu() uses internally. Note, the kmalloc_nolock() happens under bpf_spin_lock_irqsave(), so it will always fail in PREEMPT_RT. This is not an issue at the moment, since bpf_timers are disabled in PREEMPT_RT. In the future bpf_spin_lock will be replaced with state machine similar to bpf_task_work. Fixes: 6d78b4473cdb ("bpf: Tell memcg to use allow_spinning=false path in bpf_timer_init()") Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Reviewed-by: Shakeel Butt Acked-by: Harry Yoo Acked-by: Vlastimil Babka Cc: linux-mm@kvack.org Link: https://lore.kernel.org/bpf/20251015000700.28988-1-alexei.starovoitov@gmail.com --- include/linux/bpf.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index a98c83346134..d808253f2e94 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2499,6 +2499,8 @@ int bpf_map_alloc_pages(const struct bpf_map *map, int nid, #ifdef CONFIG_MEMCG void *bpf_map_kmalloc_node(const struct bpf_map *map, size_t size, gfp_t flags, int node); +void *bpf_map_kmalloc_nolock(const struct bpf_map *map, size_t size, gfp_t flags, + int node); void *bpf_map_kzalloc(const struct bpf_map *map, size_t size, gfp_t flags); void *bpf_map_kvcalloc(struct bpf_map *map, size_t n, size_t size, gfp_t flags); @@ -2511,6 +2513,8 @@ void __percpu *bpf_map_alloc_percpu(const struct bpf_map *map, size_t size, */ #define bpf_map_kmalloc_node(_map, _size, _flags, _node) \ kmalloc_node(_size, _flags, _node) +#define bpf_map_kmalloc_nolock(_map, _size, _flags, _node) \ + kmalloc_nolock(_size, _flags, _node) #define bpf_map_kzalloc(_map, _size, _flags) \ kzalloc(_size, _flags) #define bpf_map_kvcalloc(_map, _n, _size, _flags) \ -- cgit v1.2.3