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[71.206.142.238]) by smtp.gmail.com with ESMTPSA id c7-20020a0cd607000000b005ef493c6bebsm1604549qvj.77.2023.05.10.08.32.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 May 2023 08:32:32 -0700 (PDT) To: libc-alpha@sourceware.org Cc: Joe Simmons-Talbott Subject: [PATCH v2] vfprintf-internal: Replace alloca with malloc. Date: Wed, 10 May 2023 11:32:30 -0400 Message-Id: <20230510153230.2207571-1-josimmon@redhat.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.1 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Joe Simmons-Talbott via Libc-alpha From: Joe Simmons-Talbott Reply-To: Joe Simmons-Talbott Errors-To: libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org Sender: "Libc-alpha" Avoid potential stack overflow from unbounded alloca. --- Changes to v1: * Don't check pointer before calling free() * Move deallocation code after the all_done label stdio-common/vfprintf-internal.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/stdio-common/vfprintf-internal.c b/stdio-common/vfprintf-internal.c index c76c06e49b..58c21481ce 100644 --- a/stdio-common/vfprintf-internal.c +++ b/stdio-common/vfprintf-internal.c @@ -1001,6 +1001,7 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format, scratch_buffer_init (&specsbuf); struct printf_spec *specs = specsbuf.data; size_t specs_limit = specsbuf.length / sizeof (specs[0]); + bool malloced_pa_user = false; /* Used as a backing store for args_value, args_size, args_type below. */ @@ -1171,7 +1172,10 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format, else if (__glibc_unlikely (__printf_va_arg_table != NULL) && __printf_va_arg_table[args_type[cnt] - PA_LAST] != NULL) { - args_value[cnt].pa_user = alloca (args_size[cnt]); + args_value[cnt].pa_user = malloc (args_size[cnt]); + if (args_value[cnt].pa_user == NULL) + break; + malloced_pa_user = true; (*__printf_va_arg_table[args_type[cnt] - PA_LAST]) (args_value[cnt].pa_user, ap_savep); } @@ -1334,7 +1338,11 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format, (specs[nspecs_done].next_fmt - specs[nspecs_done].end_of_fmt)); } all_done: + if (malloced_pa_user) + for (cnt = 0; cnt < nargs; ++cnt) + free (args_value[cnt].pa_user); scratch_buffer_free (&argsbuf); scratch_buffer_free (&specsbuf); } -- 2.39.2