Running: $ valgrind ./xgcc -B. -c test.c -march=native on aarch64 shows a use-after-free in host_detect_local_cpu due to the std::string result of aarch64_get_extension_string_for_isa_flags only living until immediately after a c_str call.
This leads to corrupt "-march=" values being passed to cc1. This patch fixes the use-after-free, though it appears to also need Tamar's patch here: https://gcc.gnu.org/ml/gcc-patches/2018-12/msg01302.html in order to generate valid values for cc1. This may have worked by accident in the past, if the corrupt "-march=" value happened to be 0-terminated in the "right" place; with this patch it now appears to reliably break without Tamar's patch. Lightly tested: I've manually verified that this cleans up the valgrind output for the driver, but I haven't bootstrapped with it. OK for trunk? gcc/ChangeLog: PR driver/89014 * config/aarch64/driver-aarch64.c (host_detect_local_cpu): Fix use-after-free of the result of aarch64_get_extension_string_for_isa_flags. --- gcc/config/aarch64/driver-aarch64.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/gcc/config/aarch64/driver-aarch64.c b/gcc/config/aarch64/driver-aarch64.c index 2bf1f9a..100e0c3 100644 --- a/gcc/config/aarch64/driver-aarch64.c +++ b/gcc/config/aarch64/driver-aarch64.c @@ -178,7 +178,6 @@ host_detect_local_cpu (int argc, const char **argv) unsigned int variants[2] = { ALL_VARIANTS, ALL_VARIANTS }; unsigned int n_variants = 0; bool processed_exts = false; - const char *ext_string = ""; unsigned long extension_flags = 0; unsigned long default_flags = 0; @@ -348,11 +347,12 @@ host_detect_local_cpu (int argc, const char **argv) if (tune) return res; - ext_string - = aarch64_get_extension_string_for_isa_flags (extension_flags, - default_flags).c_str (); - - res = concat (res, ext_string, NULL); + { + std::string extension + = aarch64_get_extension_string_for_isa_flags (extension_flags, + default_flags); + res = concat (res, extension.c_str (), NULL); + } return res; -- 1.8.5.3
