6.6-stable review patch. If anyone has any objections, please let me know.
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From: Martin KaFai Lau martin.lau@kernel.org
[ Upstream commit 8eef6ac4d70eb1f0099fff93321d90ce8fa49ee1 ]
In PREEMPT_RT, kmalloc(GFP_ATOMIC) is still not safe in non preemptible context. bpf_mem_alloc must be used in PREEMPT_RT. This patch is to enforce bpf_mem_alloc in the bpf_local_storage when CONFIG_PREEMPT_RT is enabled.
[ 35.118559] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 [ 35.118566] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1832, name: test_progs [ 35.118569] preempt_count: 1, expected: 0 [ 35.118571] RCU nest depth: 1, expected: 1 [ 35.118577] INFO: lockdep is turned off. ... [ 35.118647] __might_resched+0x433/0x5b0 [ 35.118677] rt_spin_lock+0xc3/0x290 [ 35.118700] ___slab_alloc+0x72/0xc40 [ 35.118723] __kmalloc_noprof+0x13f/0x4e0 [ 35.118732] bpf_map_kzalloc+0xe5/0x220 [ 35.118740] bpf_selem_alloc+0x1d2/0x7b0 [ 35.118755] bpf_local_storage_update+0x2fa/0x8b0 [ 35.118784] bpf_sk_storage_get_tracing+0x15a/0x1d0 [ 35.118791] bpf_prog_9a118d86fca78ebb_trace_inet_sock_set_state+0x44/0x66 [ 35.118795] bpf_trace_run3+0x222/0x400 [ 35.118820] __bpf_trace_inet_sock_set_state+0x11/0x20 [ 35.118824] trace_inet_sock_set_state+0x112/0x130 [ 35.118830] inet_sk_state_store+0x41/0x90 [ 35.118836] tcp_set_state+0x3b3/0x640
There is no need to adjust the gfp_flags passing to the bpf_mem_cache_alloc_flags() which only honors the GFP_KERNEL. The verifier has ensured GFP_KERNEL is passed only in sleepable context.
It has been an old issue since the first introduction of the bpf_local_storage ~5 years ago, so this patch targets the bpf-next.
bpf_mem_alloc is needed to solve it, so the Fixes tag is set to the commit when bpf_mem_alloc was first used in the bpf_local_storage.
Fixes: 08a7ce384e33 ("bpf: Use bpf_mem_cache_alloc/free in bpf_local_storage_elem") Reported-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Link: https://lore.kernel.org/r/20241218193000.2084281-1-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/bpf_local_storage.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index e8d02212da703..b4c6b9b3cb421 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -823,8 +823,12 @@ bpf_local_storage_map_alloc(union bpf_attr *attr, smap->elem_size = offsetof(struct bpf_local_storage_elem, sdata.data[attr->value_size]);
- smap->bpf_ma = bpf_ma; - if (bpf_ma) { + /* In PREEMPT_RT, kmalloc(GFP_ATOMIC) is still not safe in non + * preemptible context. Thus, enforce all storages to use + * bpf_mem_alloc when CONFIG_PREEMPT_RT is enabled. + */ + smap->bpf_ma = IS_ENABLED(CONFIG_PREEMPT_RT) ? true : bpf_ma; + if (smap->bpf_ma) { err = bpf_mem_alloc_init(&smap->selem_ma, smap->elem_size, false); if (err) goto free_smap;