From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1E7AB28505E; Thu, 16 Jul 2026 14:14:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784211271; cv=none; b=C7iWJMAAqE2Sw2SRxCQfVoHkv4W9M6EjnM6rWnXuu/48epovEGXNBE/j+9XBSn10d/oxpXci6HyAQT9qtaB1iCkYq/BRD9NHebGukQOFoHib9eRvmIIgxZjOKJBqLnbcP++ZF/HmgYgW/DCN+bGNre7Cvgwco/Tcal22CnS2eVw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784211271; c=relaxed/simple; bh=XjyeqK70nPsnYq7nIYqM66/gsVzLKV1RIA7Wzghk04A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HiP5OCz+nUue1E8z6jr8VWUMKovlzvQBbwd22VxGUuaaZVkn0s5YusXkFor5Cv3QokSQViq2YamEB56TDe/lNxsQ70C0zQ9hV1sz8YEuGOHFOpvHm1HTKS8Th0Twbdk7f/0ulJ3swlvhh5CjJnmdkf3DwJTo2TV1Hl9LeHa08BE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XyDEAITU; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="XyDEAITU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 839271F00A3A; Thu, 16 Jul 2026 14:14:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784211270; bh=GM/JoFIsOAenAHVdSWncGJOn+AaulQCO3YLkwoVIXSw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XyDEAITUvXHQP9YqW6niXCXWhi5tZ2r7i4wequp9Yu5KlnNTTHzB08MfEPw/pZkWG 8LPHCwlnby3zvqdePVfAIkHBxiBMSNuvNjrSoPNohTE+8FcI3gCQ3oObueAVfkSoWn zAWbbnz7ExEEja0RDU4UbnsUmsYQzsIbmEqHgH1c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Pawan Gupta , Daniel Borkmann , Sasha Levin Subject: [PATCH 6.18 327/480] bpf: Restrict JIT predictor flush to cBPF Date: Thu, 16 Jul 2026 15:31:14 +0200 Message-ID: <20260716133051.893012611@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133044.672218725@linuxfoundation.org> References: <20260716133044.672218725@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pawan Gupta commit 0bb99f2cfaae6822d734d69722de30af823efdf3 upstream. Currently predictor flush on memory reuse is done for all BPF JIT allocations, but only cBPF programs can be loaded by an unprivileged user. eBPF is privileged by default, and flushing predictors for all CPUs on every eBPF reuse penalizes the common case for no security benefit. eBPF allocations can be frequent on busy systems, only flush predictors for cBPF programs. Trampoline and dispatcher allocations also skip the flush as they are eBPF-only. [pawan: backport had various conflicts in arches bpf_int_jit_compile(). loongarch bpf_int_jit_compile() doesn't use pack allocator, dropped was_classic hunk. ] Signed-off-by: Pawan Gupta Acked-by: Daniel Borkmann Signed-off-by: Daniel Borkmann Signed-off-by: Sasha Levin --- arch/arm64/net/bpf_jit_comp.c | 4 ++-- arch/loongarch/net/bpf_jit.c | 2 +- arch/powerpc/net/bpf_jit_comp.c | 4 ++-- arch/riscv/net/bpf_jit_comp64.c | 2 +- arch/riscv/net/bpf_jit_core.c | 3 ++- arch/x86/net/bpf_jit_comp.c | 5 +++-- include/linux/filter.h | 5 +++-- kernel/bpf/core.c | 13 ++++++++----- kernel/bpf/dispatcher.c | 2 +- 9 files changed, 23 insertions(+), 17 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 873c1b784a872d..c563bae8fce1c2 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -2117,7 +2117,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) image_size = extable_offset + extable_size; ro_header = bpf_jit_binary_pack_alloc(image_size, &ro_image_ptr, sizeof(u64), &header, &image_ptr, - jit_fill_hole); + jit_fill_hole, was_classic); if (!ro_header) { prog = orig_prog; goto out_off; @@ -2754,7 +2754,7 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags, void *arch_alloc_bpf_trampoline(unsigned int size) { - return bpf_prog_pack_alloc(size, jit_fill_hole); + return bpf_prog_pack_alloc(size, jit_fill_hole, false); } void arch_free_bpf_trampoline(void *image, unsigned int size) diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index e9d666508ae28f..a000620ca99da7 100644 --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -1474,7 +1474,7 @@ static void invoke_bpf_mod_ret(struct jit_ctx *ctx, struct bpf_tramp_links *tl, void *arch_alloc_bpf_trampoline(unsigned int size) { - return bpf_prog_pack_alloc(size, jit_fill_hole); + return bpf_prog_pack_alloc(size, jit_fill_hole, false); } void arch_free_bpf_trampoline(void *image, unsigned int size) diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c index 189ef7b72081d2..cedab25aa3a823 100644 --- a/arch/powerpc/net/bpf_jit_comp.c +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -246,7 +246,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len; fhdr = bpf_jit_binary_pack_alloc(alloclen, &fimage, 4, &hdr, &image, - bpf_jit_fill_ill_insns); + bpf_jit_fill_ill_insns, bpf_prog_was_classic(fp)); if (!fhdr) { fp = org_fp; goto out_addrs; @@ -468,7 +468,7 @@ bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena) void *arch_alloc_bpf_trampoline(unsigned int size) { - return bpf_prog_pack_alloc(size, bpf_jit_fill_ill_insns); + return bpf_prog_pack_alloc(size, bpf_jit_fill_ill_insns, false); } void arch_free_bpf_trampoline(void *image, unsigned int size) diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 45cbc7c6fe490c..9e9e6dcfc48254 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -1268,7 +1268,7 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags, void *arch_alloc_bpf_trampoline(unsigned int size) { - return bpf_prog_pack_alloc(size, bpf_fill_ill_insns); + return bpf_prog_pack_alloc(size, bpf_fill_ill_insns, false); } void arch_free_bpf_trampoline(void *image, unsigned int size) diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c index 191bf0e66c8243..e4ab5bb9c9f646 100644 --- a/arch/riscv/net/bpf_jit_core.c +++ b/arch/riscv/net/bpf_jit_core.c @@ -125,7 +125,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) bpf_jit_binary_pack_alloc(prog_size + extable_size, &jit_data->ro_image, sizeof(u32), &jit_data->header, &jit_data->image, - bpf_fill_ill_insns); + bpf_fill_ill_insns, + bpf_prog_was_classic(prog)); if (!jit_data->ro_header) { prog = orig_prog; goto out_offset; diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 788671a32d8ee0..c3798cab3b7db0 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -3447,7 +3447,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im void *arch_alloc_bpf_trampoline(unsigned int size) { - return bpf_prog_pack_alloc(size, jit_fill_hole); + return bpf_prog_pack_alloc(size, jit_fill_hole, false); } void arch_free_bpf_trampoline(void *image, unsigned int size) @@ -3780,7 +3780,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) /* allocate module memory for x86 insns and extable */ header = bpf_jit_binary_pack_alloc(roundup(proglen, align) + extable_size, &image, align, &rw_header, &rw_image, - jit_fill_hole); + jit_fill_hole, + bpf_prog_was_classic(prog)); if (!header) { prog = orig_prog; goto out_addrs; diff --git a/include/linux/filter.h b/include/linux/filter.h index 3c4dd718beced8..2469fd2e401578 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -1290,7 +1290,7 @@ void bpf_jit_free(struct bpf_prog *fp); struct bpf_binary_header * bpf_jit_binary_pack_hdr(const struct bpf_prog *fp); -void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns); +void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns, bool was_classic); void bpf_prog_pack_free(void *ptr, u32 size); static inline bool bpf_prog_kallsyms_verify_off(const struct bpf_prog *fp) @@ -1304,7 +1304,8 @@ bpf_jit_binary_pack_alloc(unsigned int proglen, u8 **ro_image, unsigned int alignment, struct bpf_binary_header **rw_hdr, u8 **rw_image, - bpf_jit_fill_hole_t bpf_fill_ill_insns); + bpf_jit_fill_hole_t bpf_fill_ill_insns, + bool was_classic); int bpf_jit_binary_pack_finalize(struct bpf_binary_header *ro_header, struct bpf_binary_header *rw_header); void bpf_jit_binary_pack_free(struct bpf_binary_header *ro_header, diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index a043fccb917e86..338a806e25c045 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -924,7 +924,7 @@ static struct bpf_prog_pack *alloc_new_pack(bpf_jit_fill_hole_t bpf_fill_ill_ins return NULL; } -void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns) +void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns, bool was_classic) { unsigned int nbits = BPF_PROG_SIZE_TO_NBITS(size); struct bpf_prog_pack *pack; @@ -939,7 +939,7 @@ void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns) * safe because cBPF programs (the unprivileged attack surface) * are bounded well below a pack size. */ - if (static_branch_unlikely(&bpf_pred_flush_enabled)) + if (was_classic && static_branch_unlikely(&bpf_pred_flush_enabled)) pr_warn_once("BPF: Predictors not flushed for allocations greater than BPF_PROG_PACK_SIZE\n"); size = round_up(size, PAGE_SIZE); ptr = bpf_jit_alloc_exec(size); @@ -971,7 +971,9 @@ void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns) pos = 0; found_free_area: - static_call_cond(bpf_arch_pred_flush)(); + /* Flush only for cBPF as it may contain a crafted gadget */ + if (static_branch_unlikely(&bpf_pred_flush_enabled) && was_classic) + static_call_cond(bpf_arch_pred_flush)(); bitmap_set(pack->bitmap, pos, nbits); ptr = (void *)(pack->ptr) + (pos << BPF_PROG_CHUNK_SHIFT); @@ -1131,7 +1133,8 @@ bpf_jit_binary_pack_alloc(unsigned int proglen, u8 **image_ptr, unsigned int alignment, struct bpf_binary_header **rw_header, u8 **rw_image, - bpf_jit_fill_hole_t bpf_fill_ill_insns) + bpf_jit_fill_hole_t bpf_fill_ill_insns, + bool was_classic) { struct bpf_binary_header *ro_header; u32 size, hole, start; @@ -1144,7 +1147,7 @@ bpf_jit_binary_pack_alloc(unsigned int proglen, u8 **image_ptr, if (bpf_jit_charge_modmem(size)) return NULL; - ro_header = bpf_prog_pack_alloc(size, bpf_fill_ill_insns); + ro_header = bpf_prog_pack_alloc(size, bpf_fill_ill_insns, was_classic); if (!ro_header) { bpf_jit_uncharge_modmem(size); return NULL; diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index b77db7413f8c70..ea2d60dc1feeb7 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c @@ -145,7 +145,7 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from, mutex_lock(&d->mutex); if (!d->image) { - d->image = bpf_prog_pack_alloc(PAGE_SIZE, bpf_jit_fill_hole_with_zero); + d->image = bpf_prog_pack_alloc(PAGE_SIZE, bpf_jit_fill_hole_with_zero, false); if (!d->image) goto out; d->rw_image = bpf_jit_alloc_exec(PAGE_SIZE); -- 2.53.0