From 879b71d6e95673e58d33f6c3c341a893ee307161 Mon Sep 17 00:00:00 2001 From: Alexey Sheplyakov Date: Sat, 10 Jul 2021 22:18:14 +0400 Subject: [PATCH] dcc_gcc_rewrite_fqn: avoid heap corruption On ALT Linux I've run into the following bug: distcc gcc -Wall -std=gnu89 -I. -O2 -o hello.o -c hello.c free(): invalid next size (fast) Aborted (core dumped) Apparently dcc_gcc_rewrite writes beyond the allocated memory: valgrind --leak-check=full -v ./distcc gcc -Wall -std=gnu89 -I. -O2 -o hello.o -c hello.c ==11382== ERROR SUMMARY: 53 errors from 5 contexts (suppressed: 0 from 0) ==11382== ==11382== 1 errors in context 1 of 5: ==11382== Invalid write of size 1 ==11382== at 0x4C349D8: strcat (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==11382== by 0x10D165: dcc_gcc_rewrite_fqn (compile.c:611) ==11382== by 0x10D4B4: dcc_build_somewhere (compile.c:725) ==11382== by 0x10DC01: dcc_build_somewhere_timed (compile.c:1014) ==11382== by 0x10E380: main (distcc.c:352) ==11382== Address 0x544e828 is 1 bytes after a block of size 23 alloc'd ==11382== at 0x4C31B0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==11382== by 0x10D087: dcc_gcc_rewrite_fqn (compile.c:588) ==11382== by 0x10D4B4: dcc_build_somewhere (compile.c:725) ==11382== by 0x10DC01: dcc_build_somewhere_timed (compile.c:1014) ==11382== by 0x10E380: main (distcc.c:352) ==11382== ==11382== ==11382== 1 errors in context 2 of 5: ==11382== Invalid write of size 1 ==11382== at 0x4C349C8: strcat (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==11382== by 0x10D165: dcc_gcc_rewrite_fqn (compile.c:611) ==11382== by 0x10D4B4: dcc_build_somewhere (compile.c:725) ==11382== by 0x10DC01: dcc_build_somewhere_timed (compile.c:1014) ==11382== by 0x10E380: main (distcc.c:352) ==11382== Address 0x544e827 is 0 bytes after a block of size 23 alloc'd ==11382== at 0x4C31B0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==11382== by 0x10D087: dcc_gcc_rewrite_fqn (compile.c:588) ==11382== by 0x10D4B4: dcc_build_somewhere (compile.c:725) ==11382== by 0x10DC01: dcc_build_somewhere_timed (compile.c:1014) ==11382== by 0x10E380: main (distcc.c:352) and ALT Linux' hardened glibc does not quite like that. Correctly compute the `newcmd_len` to avoid the problem. ALTBUG: #40425 --- src/compile.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/compile.c b/src/compile.c index 34964566..26d7d182 100644 --- a/src/compile.c +++ b/src/compile.c @@ -584,7 +584,7 @@ static int dcc_gcc_rewrite_fqn(char **argv) return -ENOENT; - newcmd_len = strlen(target_with_vendor) + 1 + strlen(argv[0] + 1); + newcmd_len = strlen(target_with_vendor) + 1 + strlen(argv[0]) + 1; newcmd = malloc(newcmd_len); if (!newcmd) return -ENOMEM;