GC guard lookup_name

peterzhu2118 · peterzhu2118 · commit 36966456c728 · 2024-12-20T16:52:36.000-05:00
When searching for native extensions, if the name does not end in ".so" then we create a new string and append ".so" so it. If the native extension is in static_ext_inits, then we could trigger a GC in the rb_filesystem_str_new_cstr. This could cuase the GC to free lookup_name since we don't use the local variable anymore. This bug was caught in this ASAN build: http://ci.rvm.jp/results/trunk_asan@ruby-sp1/5479182 ==435614==ERROR: AddressSanitizer: use-after-poison on address 0x715a63022da0 at pc 0x5e7463873e4e bp 0x7fff383c8b00 sp 0x7fff383c82c0 READ of size 14 at 0x715a63022da0 thread T0 #0 0x5e7463873e4d in __asan_memcpy (/tmp/ruby/build/trunk_asan/ruby+0x214e4d) (BuildId: 607411c0626a2f66b4c20c02179b346aace20898) #1 0x5e7463b50a82 in memcpy /usr/include/x86_64-linux-gnu/bits/string_fortified.h:29:10 #2 0x5e7463b50a82 in ruby_nonempty_memcpy /tmp/ruby/src/trunk_asan/include/ruby/internal/memory.h:671:16 #3 0x5e7463b50a82 in str_enc_new /tmp/ruby/src/trunk_asan/string.c:1035:9 #4 0x5e74639b97dd in search_required /tmp/ruby/src/trunk_asan/load.c:1126:21 #5 0x5e74639b97dd in require_internal /tmp/ruby/src/trunk_asan/load.c:1274:17 #6 0x5e74639b83c1 in rb_require_string_internal /tmp/ruby/src/trunk_asan/load.c:1401:22 #7 0x5e74639b83c1 in rb_require_string /tmp/ruby/src/trunk_asan/load.c:1387:12
diff --git a/load.c b/load.c
@@ -1124,6 +1124,7 @@ search_required(rb_vm_t *vm, VALUE fname, volatile VALUE *path, feature_func rb_
         ftptr = RSTRING_PTR(lookup_name);
         if (st_lookup(vm->static_ext_inits, (st_data_t)ftptr, NULL)) {
             *path = rb_filesystem_str_new_cstr(ftptr);
+            RB_GC_GUARD(lookup_name);
             return 's';
         }
     }

Original file line number	Diff line number	Diff line change
`@@ -1124,6 +1124,7 @@ search_required(rb_vm_t vm, VALUE fname, volatile VALUE path, feature_func rb_`
`1124`	`1124`	`ftptr = RSTRING_PTR(lookup_name);`
`1125`	`1125`	`if (st_lookup(vm->static_ext_inits, (st_data_t)ftptr, NULL)) {`
`1126`	`1126`	`*path = rb_filesystem_str_new_cstr(ftptr);`
	`1127`	`+ RB_GC_GUARD(lookup_name);`
`1127`	`1128`	`return 's';`
`1128`	`1129`	`}`
`1129`	`1130`	`}`