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([2804:1b3:a7c2:2485:a9ff:45ba:83f5:84f5]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-311747f598dsm517650eec.6.2026.07.06.14.15.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Jul 2026 14:15:29 -0700 (PDT) From: Adhemerval Zanella To: libc-alpha@sourceware.org Cc: "Andreas K . Huettel" , DJ Delorie Subject: [PATCH 1/8] elf: Bound the tunable cache string table against the mapping size Date: Mon, 6 Jul 2026 18:14:37 -0300 Message-ID: <20260706211524.3801466-2-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260706211524.3801466-1-adhemerval.zanella@linaro.org> References: <20260706211524.3801466-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-12.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_NONE, TXREP shortcircuit=no autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces~patchwork=sourceware.org@sourceware.org _dl_load_cache_tunables bounds each entry's string offsets against [s_start, start + cache_new->len_strings], but len_strings is an unvalidated 32-bit field from ld.so.cache and s_start/s_end were int. A corrupt cache with an oversized len_strings could make s_end exceed the mapping (or overflow), letting an offset point outside the mmap; the following strcmp/__strdup would then read unmapped memory. Compute the offsets as size_t and clamp s_end to cachesize, matching how the regular library lookup bounds string offsets against the mapping size. Checked on x86_64-linux-gnu and i686-linux-gnu. Reviewed-by: DJ Delorie --- elf/dl-cache.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/elf/dl-cache.c b/elf/dl-cache.c index d05afe27004..5d8d3cae908 100644 --- a/elf/dl-cache.c +++ b/elf/dl-cache.c @@ -17,6 +17,7 @@ . */ #include +#include #include #include #include @@ -649,9 +650,16 @@ _dl_load_cache_tunables (const char **data) != (void *) & tec[count]) return NULL; - /* Validate each entry. */ - int s_start = (const char *) (&cache_new->libs[cache_new->nlibs]) - *data; - int s_end = s_start + cache_new->len_strings; + /* Validate each entry. The string table lies between the file entries + and the end of the mapping; clamp its end to CACHESIZE so that a bogus + len_strings cannot make an offset point outside the mapped file. */ + size_t s_start = (const char *) (&cache_new->libs[cache_new->nlibs]) - *data; + size_t s_end; + if (s_start >= cachesize + || INT_ADD_WRAPV (s_start, cache_new->len_strings, &s_end)) + return NULL; + if (s_end > cachesize) + s_end = cachesize; for (i = 0; i < count; i ++) { if (thc->tunables[i].name_offset < s_start