[Crash-utility] [PATCH] extension: Fix crash segfaults when loading same extension with different names twice

[Tao Liu]

If a same extension(Eg: extensions/trace.so) with two different names are loaded by
"extend" command twice, it sometimes segfaults crash.

It's because crash uses RTLD_NOW|RTLD_GLOBAL flags of dlopen to load an extension.
RTDL_GLOBAL will make symbols defined by this shared object available for
symbol resolution of subsequently loaded shared objects. So symbols with the same
name will be exported from the former to the latter. In this case, when 2 extensions
only differ from file names, the subsequently loaded extension will have unexpected
initial values for global varibles.

This patch adds RTLD_DEEPBIND flag to dlopen, making extensions using its
own symbols preference to symbols with the same name contained by others.

Signed-off-by: Tao Liu <ltao at redhat.com>
---
 extensions.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/extensions.c b/extensions.c
index d23b1e3..e07f9a9 100644
--- a/extensions.c
+++ b/extensions.c
@@ -317,7 +317,7 @@ load_extension(char *lib)
         *  _init() function before dlopen() returns below.
 	*/
 	pc->curext = ext;
-	ext->handle = dlopen(ext->filename, RTLD_NOW|RTLD_GLOBAL); 
+	ext->handle = dlopen(ext->filename, RTLD_NOW|RTLD_GLOBAL|RTLD_DEEPBIND);
 
 	if (!ext->handle) {
 		strcpy(buf, dlerror());
-- 
2.29.2