From nobody Fri Sep 25 01:20:51 2026 Received: from out28-1.mail.aliyun.com (out28-1.mail.aliyun.com [115.124.28.1]) (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 525D54D1794; Thu, 17 Sep 2026 19:11:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.28.1 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789672306; cv=none; b=hpnHWRyTs1GfWcrxh7vyea51wSEsWnjcEc2N+hViCIbbh/Byom5IsMM+Ss/InFJTKGYm/nvQAjyp8DQ9psEjXLt8iPkltPHMhpFCmQ0Xc/GGTv0sxH7GGQiEEEcjKBzydlGBBM6zem/uZdSZ0/NgtCTA2zr019+yxY7TcVO33J8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789672306; c=relaxed/simple; bh=ZOmNJmrIMk3u5pxEOy2Rj23mM2c5qnvtPoFKoM/HxOE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Y4eZ8YCuW2TfEXqcLWh8Ck763q2lBdy1otXP7RvdgEjHgLB0l90pjwBwlb0gvyM8eW+CqPfHqyeuIov42thGy+7GYYRsWrYRIaxngC2FVA9rKG8VdvrmE8XYsLs+8WBLEclBGbUVckLzo4K6ry/GC/CflMnSZlFgFho4e78Dpx8= 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=Eq2AYVbh; arc=none smtp.client-ip=115.124.28.1 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="Eq2AYVbh" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xiaopeng.com; s=default; t=1789672302; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=txpFZbn8I2u3+SIACXugxhsg4q5nyadngQpza3Bq2As=; b=Eq2AYVbhvHBZ/4/ZChX+CrQ1o9Faa5W6Kz6FgfIRYSe8tad+Dam+UzRIJgADZK9Gtjdw7b2vEsJflJl6RhGfLWtwiTFIt77exZfvzN7I7vN5bJZJdKpBafKZoTG64W12k1SSMPkp7dbp1UaeVpErRUzoaBwChJKotGA77hjQHC4= X-Alimail-AntiSpam: AC=CONTINUE;BC=0.04436491|-1;CH=green;DM=|CONTINUE|false|;DS=CONTINUE|ham_system_inform|0.00685537-0.000624417-0.99252;FP=3450452327357023579|12|2|11|0|-1|-1|-1;HT=maildocker-contentspam033037022039;MF=fangxy@xiaopeng.com;NM=1;PH=DS;RN=10;RT=10;SR=0;TI=SMTPD_---.jG9ODgi_1789671980; Received: from localhost.localdomain(mailfrom:fangxy@xiaopeng.com fp:SMTPD_---.jG9ODgi_1789671980 cluster:ay29) by smtp.aliyun-inc.com; Fri, 18 Sep 2026 03:06:21 +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 v2 1/2] module: Sanitize the undefined sh_name of SHT_NULL sections Date: Fri, 18 Sep 2026 03:06:17 +0800 Message-ID: <20260917190618.94759-2-fangxy@xiaopeng.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260917190618.94759-1-fangxy@xiaopeng.com> References: <20260917190618.94759-1-fangxy@xiaopeng.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" elf_validity_cache_secstrings() skips the sh_name bounds check for a SHT_NULL section: for (i =3D 0; i < info->hdr->e_shnum; i++) { shdr =3D &info->sechdrs[i]; /* SHT_NULL means sh_name has an undefined value */ if (shdr->sh_type =3D=3D SHT_NULL) continue; if (shdr->sh_name >=3D 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 =3D 1; i < info->hdr->e_shnum; i++) { if (strcmp(info->secstrings + info->sechdrs[i].sh_name, name) =3D=3D 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_secstring= s() 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 le= aves 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 "" an= d, as before, is ignored, so the module loads with rc=3D0. Both cases ran on 704340f1cd0d (9 commits past v7.3-rc3): 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 a= nd 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 bu= ilt 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) =20 for (i =3D 0; i < info->hdr->e_shnum; i++) { shdr =3D &info->sechdrs[i]; - /* SHT_NULL means sh_name has an undefined value */ - if (shdr->sh_type =3D=3D 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 =3D=3D SHT_NULL) { + shdr->sh_name =3D 0; continue; + } if (shdr->sh_name >=3D strhdr->sh_size) { pr_err("Invalid ELF section name in module (section %u type %u)\n", i, shdr->sh_type); --=20 2.50.1 (Apple Git-155) From nobody Fri Sep 25 01:20:51 2026 Received: from out28-2.mail.aliyun.com (out28-2.mail.aliyun.com [115.124.28.2]) (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 5BC3A3C9886; Thu, 17 Sep 2026 19:06:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.28.2 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; 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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="lNCbfOWH" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xiaopeng.com; s=default; t=1789671982; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=j4f31wokbPC278wohUMG2oItib2vdp0SWcrWkefjH1s=; b=lNCbfOWH0bwXO/MISLbxGZIB5WMDy+AbE+4BDQHA0KHlIb5Goe8PRtZtaVGYtIWiESXBjsdGrsuMudkT5zTLziCtFcv9CIM9UoUhQMhXarV/aejaYW1+qJwY/e/x1KM7LLSx+3/sxoZNMXdLVWzalIxtQpYDDiRgRn83vJyDjX0= X-Alimail-AntiSpam: AC=CONTINUE;BC=0.04436274|-1;CH=green;DM=|CONTINUE|false|;DS=CONTINUE|ham_system_inform|0.0473385-0.000483961-0.952178;FP=5594062516591330395|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_---.jG9ODhh_1789671981; Received: from localhost.localdomain(mailfrom:fangxy@xiaopeng.com fp:SMTPD_---.jG9ODhh_1789671981 cluster:ay29) by smtp.aliyun-inc.com; Fri, 18 Sep 2026 03:06:22 +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 v2 2/2] module: Validate the __version_ext_names section type Date: Fri, 18 Sep 2026 03:06:18 +0800 Message-ID: <20260917190618.94759-3-fangxy@xiaopeng.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260917190618.94759-1-fangxy@xiaopeng.com> References: <20260917190618.94759-1-fangxy@xiaopeng.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" elf_validity_check_sectionheaders() validates the size and offset of every section, unless its type is SHT_NULL or SHT_NOBITS: switch (shdr->sh_type) { case SHT_NULL: case SHT_NOBITS: /* No contents, offset/size don't mean anything */ continue; default: err =3D validate_section_offset(info, shdr); elf_validity_cache_index_versions() then reads the extended version names by their sh_offset, without checking that the section holds data: if (vers_ext_crc) { crc_count =3D info->sechdrs[vers_ext_crc].sh_size / sizeof(u32); name =3D (void *)info->hdr + info->sechdrs[vers_ext_name].sh_offset; remaining_len =3D info->sechdrs[vers_ext_name].sh_size; while (crc_count--) { name_size =3D strnlen(name, remaining_len) + 1; A SHT_NOBITS __version_ext_names reaches here with an sh_offset the validator never bounded; past the end of the module the name lookup reads out of bounds: BUG: KASAN: vmalloc-out-of-bounds in strnlen+0x73/0x80 Read of size 1 at addr ffa00000005534ff by task insmod/79 ... strnlen+0x73/0x80 load_module+0xef6/0x8600 The buggy address belongs to a 43-page vmalloc region starting at 0xffa0000000529000 allocated at kernel_read_file+0x7b4/0x9f0 Bounding the offset is not enough: an in-bounds SHT_NOBITS section still passes it, and the walk reads unrelated file data as a version name. A real __version_ext_names is SHT_PROGBITS, whose offset elf_validity_check_sectionheaders() already bounds, so require that type and reject one holding no data, matching the string-table type checks. Fixes: 54ac1ac8edeb ("modules: Support extended MODVERSIONS info") Cc: stable@vger.kernel.org Assisted-by: Hawkeye:GLM-5.3-flash Assisted-by: Qoder:Qwen3.8-Max Signed-off-by: Fang Xieyan --- Found in the same review as patch 1/2. elf_validity_check_sectionheaders() exempts SHT_NOBITS from validate_section_offset(), and elf_validity_cache_index_versions() then dereferences the __version_ext_nam= es section as hdr + sh_offset without re-checking its type, so a section of th= at name and type SHT_NOBITS carries an unvalidated offset into the extended version name walk. This patch stands on its own; it does not depend on 1/2. v1 bounded the offset with validate_section_offset(). Review pointed out th= at is narrower than the bug: a SHT_NOBITS section whose sh_offset is in bounds still passes the bound, and the walk then reads whatever file bytes sit the= re as a version name, which violates ELF semantics (SHT_NOBITS holds no file data). v2 requires the section to be SHT_PROGBITS instead, so both the out-of-bounds and the in-bounds SHT_NOBITS cases are rejected, while a real names section (SHT_PROGBITS, already offset-checked) is unaffected. Reproducer, two variants of a .ko carrying __version_ext_crcs and a __version_ext_names of type SHT_NOBITS: - sh_offset past the end of the module image. Before: the name walk reads out of bounds (KASAN vmalloc-out-of-bounds in strnlen). After: rejected. - sh_offset in bounds, aimed at other file data (the harness points it at the relocated .shstrtab). Before: the walk silently consumes those bytes as a version name and the module is accepted; no splat fires, so a crash-only check scores it clean. After: rejected. Both variants fail insmod with -ENOEXEC (rc=3D8, "invalid module format") o= n the patched kernel, which is what a module with a malformed version section sho= uld do. Both cases ran on 704340f1cd0d (9 commits past v7.3-rc3): 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 a= nd differ only by this patch. The same vermagic caveat as patch 1/2 applies: LOCALVERSION is pinned so the patched kernel's release string matches the payload, and the loader reaches= the version walk instead of stopping at the version magic check. kernel/module/main.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/kernel/module/main.c b/kernel/module/main.c index e36bfe4..07b9dde 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -2296,6 +2296,22 @@ static int elf_validity_cache_index_versions(struct = load_info *info, int flags) * number of entries in every section. */ if (vers_ext_crc) { + /* + * The names section is read below as hdr + sh_offset, so it + * must hold file data. A real one is SHT_PROGBITS. + * elf_validity_check_sectionheaders() exempts SHT_NULL and + * SHT_NOBITS from validate_section_offset() on the assumption + * they have no contents, so a SHT_NOBITS __version_ext_names + * would reach the walk with an offset that was never bounded. + * Require the type; a SHT_PROGBITS section is already bounded + * there, so its sh_offset is safe to dereference. + */ + if (info->sechdrs[vers_ext_name].sh_type !=3D SHT_PROGBITS) { + pr_err("Invalid ELF __version_ext_names type: %u\n", + info->sechdrs[vers_ext_name].sh_type); + return -ENOEXEC; + } + crc_count =3D info->sechdrs[vers_ext_crc].sh_size / sizeof(u32); name =3D (void *)info->hdr + info->sechdrs[vers_ext_name].sh_offset; --=20 2.50.1 (Apple Git-155)