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Date: Tue, 16 Aug 2022 23:23:02 -0700
From: Elvis Pranskevichus <elvis@...edb.com>
To: musl@...ts.openwall.com
Cc: elvis@...edb.com
Subject: [RESEND PATCH] ldso/dynlink: Protect LD_ env vars from getting clobbered by apps
(sorry, the previous patch is obviously wrong, this is a better
version)
There is no guarantee that the environment block will remain intact.
For example, PostgreSQL clobbers argv/environ area to implement its
"setproctitle" emulation on non-BSD [1], and there is a popular Python
library inspired by it [2]. As a result, setting `LD_LIBRARY_PATH`
or `LD_PRELOAD` has no effect on Postgres subprocesses when linking
against musl.
Protect against this by making a copies instead of storing the original
pointers directly.
---
ldso/dynlink.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index cc677952..2b816ce0 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -1757,7 +1757,23 @@ void __dls3(size_t *sp, size_t *auxv)
/* Only trust user/env if kernel says we're not suid/sgid */
if (!libc.secure) {
env_path = getenv("LD_LIBRARY_PATH");
+ if (env_path != NULL) {
+ /* Prevent value from getting clobbered by the application */
+ env_path = strdup(env_path);
+ if (!env_path) {
+ dprintf(2, "%s: out of memory\n", argv[0]);
+ _exit(127);
+ }
+ }
env_preload = getenv("LD_PRELOAD");
+ if (env_preload != NULL) {
+ /* Prevent value from getting clobbered by the application */
+ env_preload = strdup(env_preload);
+ if (!env_preload) {
+ dprintf(2, "%s: out of memory\n", argv[0]);
+ _exit(127);
+ }
+ }
}
/* Activate error handler function */
--
2.35.1
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