On 11/1/24 1:18 PM, Alexei Starovoitov wrote:
On Thu, Oct 31, 2024 at 8:10 PM Yonghong Song <yonghong.song@xxxxxxxxx> wrote:For any main prog or subprogs, allocate private stack space if requested by subprog info or main prog. The alignment for private stack is 16 since maximum stack alignment is 16 for bpf-enabled archs. For x86_64 arch, the allocated private stack is freed in arch specific implementation of bpf_jit_free(). Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx> --- arch/x86/net/bpf_jit_comp.c | 1 + include/linux/bpf.h | 1 + kernel/bpf/core.c | 10 ++++++++++ kernel/bpf/verifier.c | 12 ++++++++++++ 4 files changed, 24 insertions(+) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 06b080b61aa5..59d294b8dd67 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -3544,6 +3544,7 @@ void bpf_jit_free(struct bpf_prog *prog) prog->bpf_func = (void *)prog->bpf_func - cfi_get_offset(); hdr = bpf_jit_binary_pack_hdr(prog); bpf_jit_binary_pack_free(hdr, NULL); + free_percpu(prog->aux->priv_stack_ptr); WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog));I'm 99% certain there are memory leaks when free and alloc are imbalanced like this: arch code doing free while generic code doing alloc.
Indeed, there are memory leaks. See below.
} diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 8db3c5d7404b..8a3ea7440a4a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1507,6 +1507,7 @@ struct bpf_prog_aux { u32 max_rdwr_access; struct btf *attach_btf; const struct bpf_ctx_arg_aux *ctx_arg_info; + void __percpu *priv_stack_ptr; struct mutex dst_mutex; /* protects dst_* pointers below, *after* prog becomes visible */ struct bpf_prog *dst_prog; struct bpf_trampoline *dst_trampoline; diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 14d9288441f2..6905f250738b 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2396,6 +2396,7 @@ static void bpf_prog_select_func(struct bpf_prog *fp) */ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err) { + void __percpu *priv_stack_ptr; /* In case of BPF to BPF calls, verifier did all the prep * work with regards to JITing, etc. */ @@ -2421,6 +2422,15 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err) if (*err) return fp; + if (fp->aux->use_priv_stack && fp->aux->stack_depth) { + priv_stack_ptr = __alloc_percpu_gfp(fp->aux->stack_depth, 16, GFP_KERNEL); + if (!priv_stack_ptr) { + *err = -ENOMEM; + return fp; + } + fp->aux->priv_stack_ptr = priv_stack_ptr; + } + fp = bpf_int_jit_compile(fp);what happens if this jit_compile fails? Which part will free priv_stack_ptr? I suspect it's a memory leak.
Indeed. There will be a memory leak if jit failed. The same for below jit_subprogs() case. Will fix in the next revision.
bpf_prog_jit_attempt_done(fp); if (!fp->jited && jit_needed) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 596afd29f088..30e74db6a85f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -20080,6 +20080,7 @@ static int jit_subprogs(struct bpf_verifier_env *env) { struct bpf_prog *prog = env->prog, **func, *tmp; int i, j, subprog_start, subprog_end = 0, len, subprog; + void __percpu *priv_stack_ptr; struct bpf_map *map_ptr; struct bpf_insn *insn; void *old_bpf_func; @@ -20176,6 +20177,17 @@ static int jit_subprogs(struct bpf_verifier_env *env) func[i]->aux->name[0] = 'F'; func[i]->aux->stack_depth = env->subprog_info[i].stack_depth; + + if (env->subprog_info[i].use_priv_stack && func[i]->aux->stack_depth) { + priv_stack_ptr = __alloc_percpu_gfp(func[i]->aux->stack_depth, 16, + GFP_KERNEL); + if (!priv_stack_ptr) { + err = -ENOMEM; + goto out_free; + } + func[i]->aux->priv_stack_ptr = priv_stack_ptr; + } + func[i]->jit_requested = 1; func[i]->blinding_requested = prog->blinding_requested; func[i]->aux->kfunc_tab = prog->aux->kfunc_tab; -- 2.43.5
