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Tue, 28 Jul 2026 10:33:24 -0700 (PDT) Received: from localhost.localdomain ([2405:acc0:1306:9d5b:e192:4a0c:2079:ffb7]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-31504bb29b2sm802360eec.13.2026.07.28.10.33.21 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 28 Jul 2026 10:33:24 -0700 (PDT) From: Laxman Acharya Padhya To: samitolvanen@google.com, mcgrof@kernel.org, petr.pavlu@suse.com, da.gomez@kernel.org Cc: atomlin@atomlin.com, linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] module: reject malformed .modinfo sections Date: Tue, 28 Jul 2026 23:18:18 +0545 Message-ID: <20260728173318.63736-1-acharyalaxman8848@gmail.com> X-Mailer: git-send-email 2.51.2 Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit get_modinfo() and module_next_tag_pair() parse .modinfo as a sequence of NUL-terminated tag=value strings. elf_validity_cache_index_info() caches the .modinfo section index and immediately calls get_modinfo() to find the module name for early error reporting, but it does not verify that the section is non-empty or NUL-terminated first. A malformed module can therefore make the loader read past the end of .modinfo while searching for a tag. Reject empty .modinfo sections and sections that are not NUL-terminated before parsing them. Signed-off-by: Laxman Acharya Padhya --- kernel/module/main.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/kernel/module/main.c b/kernel/module/main.c index 46dd8d25a..7450319f9 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -2083,6 +2083,8 @@ static int elf_validity_cache_secstrings(struct load_info *info) static int elf_validity_cache_index_info(struct load_info *info) { int info_idx; + Elf_Shdr *info_shdr; + char *modinfo; info_idx = find_any_unique_sec(info, ".modinfo"); @@ -2096,6 +2098,18 @@ static int elf_validity_cache_index_info(struct load_info *info) } info->index.info = info_idx; + info_shdr = &info->sechdrs[info_idx]; + modinfo = (char *)info->hdr + info_shdr->sh_offset; + + if (info_shdr->sh_size == 0) { + pr_err("empty .modinfo section\n"); + return -ENOEXEC; + } + if (modinfo[info_shdr->sh_size - 1] != '\0') { + pr_err(".modinfo section isn't NUL terminated\n"); + return -ENOEXEC; + } + /* Try to find a name early so we can log errors with a module name */ info->name = get_modinfo(info, "name"); -- 2.51.2