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 86AF341DED5; Sun, 4 Oct 2026 22:52:17 +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=1791154339; cv=none; b=QRjAr7DW6aLWruzoaOC+WHJIv1dmggVHDDei+R5gvI6LJfK8kVTUEZHSYvOpjRMtPgssnTX4E4Fw96bmTM08HWCmqcnXJjqlE5YoiRlsxUdg6kNeHwJuWZJtPeBNDrc55KQZQEBvlndgSY26sDnHmrLXny1XkvVAyy+ImPUI0ZE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791154339; c=relaxed/simple; bh=1YpIQPJxSeEWFFpDwNEi3RFPDu7ZYURr8aCIeXi2MkY=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=rx0kqa/bK4l5PCEsUqITHEwksejT8OhE/6+IkGokAC76jYjzUo9Ff6xDuOqoTP3s3wa/o1sgMpGqdisdW+Oem4Bp3vX94yHqP6kph4uVLUZHzIhucJRYAwD5vPgGhXxw83D934hV4lrEp6hAeAJAAFG4bSq6UZDvBzLOkHPrJT0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lwgN3X7I; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lwgN3X7I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B80A71F000FF; Sun, 4 Oct 2026 22:52:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791154336; bh=0g2Vd/WGDWx11Z5eDEYlSIfjJcLTcCv15IHzPL8eEL8=; h=Date:From:To:cc:Subject:In-Reply-To:References; b=lwgN3X7IEPZrn04fjF+jM8fK5uE4aKHBKxjxKoexZ17Zug641RRd8T0s+2+Hq0fxT nhSzRlir695dbO4XRQ2NXQsG9vPMLy3cbt6QEfbvmLzyunDdwwqamlky1L271Kdo9R HIz5cBFDWwX+0SssHEAaBeq9fmdMylzrV2GLogS3PVfDF2dCqdzTKg7JXEXuHW2fCJ teOx/VyZCfPmU6kExhAloJQ7GUfCL4u8NysKbnAjUZ0UWLOTQA5pqsoxwOvWyeSvFe A8WJSrC86sT6PkrH8yhbd1F8VpKEL4/uqYDTBHFtPVFFHiIUzTNdoyd22ncTCiyk4i JeouYLX8Hkjjw== Date: Sun, 4 Oct 2026 16:52:12 -0600 (MDT) From: Paul Walmsley To: Wei-Jie Hung cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Mike Rapoport , Xiaofeng Yuan , Klara Modin , linux-riscv@lists.infradead.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: patch: fix handling of bpf-jit execmem addresses In-Reply-To: <20260914115607.350097-1-imbigking12@gmail.com> Message-ID: <19ff2b67-55e9-92f2-5bee-57d36a9074c4@kernel.org> References: <20260914115607.350097-1-imbigking12@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Mon, 14 Sep 2026, Wei-Jie Hung wrote: > Commit 8718e5a3090b ("riscv: patch: skip fixmap mapping when kernel text > is already writable") gated the core_kernel_text() branch of patch_map() > on CONFIG_STRICT_KERNEL_RWX, and explicitly left the vmalloc branch > unchanged. That branch has a separate problem. > > That branch only creates a temporary writable fixmap alias when > CONFIG_STRICT_MODULE_RWX is enabled, and otherwise assumes the target is > directly writable and returns the address unchanged. That assumption no > longer holds: bpf_prog_pack_alloc calls set_memory_rox() on every pack > unconditionally in alloc_new_pack(), independently of any > CONFIG_STRICT_*_RWX option, so BPF text in the vmalloc area is read-only > regardless of what CONFIG_STRICT_MODULE_RWX says. > > With CONFIG_STRICT_MODULE_RWX=n, patch_map() returns the read-only > address directly, the subsequent copy_to_kernel_nofault() takes a > page fault and returns -EFAULT. bpf_arch_text_copy() turns that into > -EINVAL, which propagates through bpf_jit_binary_pack_finalize() to the > WARN_ON() in bpf_int_jit_compile() and leaves the program un-JITed. > > Note that BPF cannot be fixed the way kprobes was in > commit bdc46e507b59 ("riscv: mm: make EXECMEM_KPROBES writable without > CONFIG_STRICT_MODULE_RWX"). EXECMEM_BPF is already PAGE_KERNEL, i.e. > writable at allocation time; the read-only mapping is established > afterwards by generic code in alloc_new_pack(), which arch code cannot > influence. The only place this can be handled is patch_map(). > > This is the same problem that was fixed on arm64 by commit b1480ed230ac > ("arm64: patching: fix handling of execmem addresses"), and the fix is > the same: CONFIG_EXECMEM is what actually tracks whether the vmalloc > area can hold executable memory that needs a temporary alias to be > written. CONFIG_BPF_JIT, CONFIG_KPROBES and CONFIG_MODULES all select > it. > > Note that this is not limited to CONFIG_MODULES=n. Unlike arm64, riscv > selects CONFIG_ARCH_OPTIONAL_KERNEL_RWX, so CONFIG_STRICT_MODULE_RWX can > be disabled with CONFIG_MODULES=y as well, and the bug is reachable in > that configuration too. > > The !CONFIG_MMU build is unaffected: it has its own __patch_insn_set() > and __patch_insn_write() implementations and never calls patch_map(). Thanks, queued for v7.3-rc. - Paul