From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out198-10.us.a.mail.aliyun.com (out198-10.us.a.mail.aliyun.com [47.90.198.10]) (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 EF6BF389E1A; Wed, 16 Sep 2026 17:48:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=47.90.198.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789580934; cv=none; b=SAI7JrVOwF0TuGJ/nC6VIBQf5Z7qHPQ0X7BuBnH9hcOFiFJxTeGfEuekqiCzM2fciXwLiBTRI7ETI1cKXTl4Ke1kCu/TlNbW+/fhn1vogFwKVHDVCgDaHgV++LQ7BrSUJAH4ObDuC03f7lCAZQuo8tpPQqjkml+UPswPy0jyx+0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789580934; c=relaxed/simple; bh=k33fXF4XusNxY5ulRNWOjlV64rtCPhIW66nonQLKaoY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uvynvH3ZK0A0GIcC4UXObm2Loae7LU8kI7qLPHuhtdpfhq3c4/imc66ZekrAt7jn9j9ugUJ6/evmvDq/V5r9Oc0cxlgLbjTdSyf48CBM1a64jjZ9RyQimDZZWKtCuGxwMFyi6Gffll9+PHGc3eI/pwk6KKWOYKnKq56ELuMTMwE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xiaopeng.com; spf=pass smtp.mailfrom=xiaopeng.com; dkim=pass (1024-bit key) header.d=xiaopeng.com header.i=@xiaopeng.com header.b=NaFB7E9g; arc=none smtp.client-ip=47.90.198.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xiaopeng.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=xiaopeng.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=xiaopeng.com header.i=@xiaopeng.com header.b="NaFB7E9g" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=xiaopeng.com; s=default; t=1789580876; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=Zx1QEPZrMvacbciA8Pq0PrXq/rwJg/pG0xocikRHfbE=; b=NaFB7E9g7Cz1b98erf7uf1QlfHCBMmiJzN6Pz3F6IByvXrQYoC/U4kGGJzWzF0MBlic/umkMXKD3QQCJzVbhRh/4RelEfKMMxdx6Y0suZpNZJ/n4sJB7bxRFYCRKG6BM+qQrOdX0QFtRjDiVBXudyz2He0v2NIpH7/e9pp2kRvc= X-Alimail-AntiSpam:AC=CONTINUE;BC=0.04436481|-1;CH=green;DM=|CONTINUE|false|;DS=CONTINUE|ham_system_inform|0.00685537-0.000624417-0.99252;FP=3450452327357023579|0|0|0|0|-1|-1|-1;HT=maildocker-contentspam033037025160;MF=fangxy@xiaopeng.com;NM=1;PH=DS;RN=10;RT=10;SR=0;TI=SMTPD_---.jFIg.Ue_1789580875; Received: from localhost.localdomain(mailfrom:fangxy@xiaopeng.com fp:SMTPD_---.jFIg.Ue_1789580875 cluster:ay29) by smtp.aliyun-inc.com; Thu, 17 Sep 2026 01:47:56 +0800 From: Fang Xieyan To: mcgrof@kernel.org, petr.pavlu@suse.com, da.gomez@kernel.org, samitolvanen@google.com, atomlin@atomlin.com Cc: mmaurer@google.com, masahiroy@kernel.org, linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 1/2] module: Sanitize the undefined sh_name of SHT_NULL sections Date: Thu, 17 Sep 2026 01:47:52 +0800 Message-ID: <20260916174753.14870-2-fangxy@xiaopeng.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260916174753.14870-1-fangxy@xiaopeng.com> References: <20260916174753.14870-1-fangxy@xiaopeng.com> Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit elf_validity_cache_secstrings() skips the sh_name bounds check for a SHT_NULL section: for (i = 0; i < info->hdr->e_shnum; i++) { shdr = &info->sechdrs[i]; /* SHT_NULL means sh_name has an undefined value */ if (shdr->sh_type == SHT_NULL) continue; if (shdr->sh_name >= strhdr->sh_size) { A SHT_NULL section may then carry an sh_name past the end of .shstrtab. The name lookups that run afterwards do not skip SHT_NULL. This is find_any_unique_sec(), which load_module() uses to locate ".modinfo": for (i = 1; i < info->hdr->e_shnum; i++) { if (strcmp(info->secstrings + info->sechdrs[i].sh_name, name) == 0) { so the out-of-bounds sh_name is read as a string. A module carrying a crafted SHT_NULL section reads past its in-memory copy: BUG: KASAN: vmalloc-out-of-bounds in strcmp+0xb0/0xc0 Read of size 1 at addr ffa00000005436e0 by task insmod/81 ... strcmp+0xb0/0xc0 find_any_unique_sec+0x103/0x190 load_module+0x5c4/0x8600 sh_name has no defined value for SHT_NULL, so give it one that is in bounds: the empty string at index 0. The walkers then compare against "" and, as before, ignore the section, so no valid module is affected. Fixes: 3c5700aeabd8 ("module: Factor out elf_validity_cache_secstrings") Cc: stable@vger.kernel.org Assisted-by: Hawkeye:GLM-5.3-flash Assisted-by: Qoder:Qwen3.8-Max Signed-off-by: Fang Xieyan --- Found by reading the section-name walkers in kernel/module/main.c after 9a5ff4568932 tightened the string-table types. elf_validity_cache_secstrings() skips the sh_name bounds check for a SHT_NULL section, but find_any_unique_sec() still resolves every section's name as secstrings + sh_name, so the skip leaves one path where an unchecked sh_name is read as a string. Patch 2/2 fixes the matching SHT_NOBITS gap on __version_ext_names; the two are independent. Reproducer: build an otherwise valid .ko and add a SHT_NULL section whose sh_name is past the end of .shstrtab (0x2000 in the run below, aimed at the redzone after the in-memory module copy). insmod it. Before the change the name lookup reads out of bounds; after it the SHT_NULL section resolves to "" and, as before, is ignored, so the module loads with rc=0. Both cases ran on 704340f1cd0d (v7.3-rc4): x86_64 defconfig plus CONFIG_KASAN_GENERIC and CONFIG_KASAN_VMALLOC, gcc 13.2.0, QEMU under TCG. The unpatched and patched kernels are built from byte-identical .config files and differ only by this patch. The tree already contains 9a5ff4568932, so this is the gap that commit left, not a re-report of it. One setup detail is not obvious. The payload has to match the kernel's vermagic to reach load_module()'s name walkers, so the patched kernel is built with LOCALVERSION pinned to keep the release string byte-identical to the unpatched one; otherwise insmod fails on the version magic before the buggy lookup ever runs and the run proves nothing. kernel/module/main.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/module/main.c b/kernel/module/main.c index d0e1e0b..e36bfe4 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -2060,9 +2060,18 @@ static int elf_validity_cache_secstrings(struct load_info *info) for (i = 0; i < info->hdr->e_shnum; i++) { shdr = &info->sechdrs[i]; - /* SHT_NULL means sh_name has an undefined value */ - if (shdr->sh_type == SHT_NULL) + /* + * SHT_NULL means sh_name has an undefined value. The section + * name walkers that follow (find_any_unique_sec(), + * module_mark_ro_after_init(), ...) look the name up as + * secstrings + sh_name for every section, so give the undefined + * value a safe in-bounds meaning instead of skipping the check: + * the empty string at index 0. + */ + if (shdr->sh_type == SHT_NULL) { + shdr->sh_name = 0; continue; + } if (shdr->sh_name >= strhdr->sh_size) { pr_err("Invalid ELF section name in module (section %u type %u)\n", i, shdr->sh_type); -- 2.50.1 (Apple Git-155)