From 9f0b452c1af4bcb54da35711eb3fa77334a350b4 Mon Sep 17 00:00:00 2001 From: Mathias Fiedler Date: Fri, 23 Aug 2019 12:46:48 +0200 Subject: [PATCH] cve-2017-17052: Avoid unsafe exits in threads According to manpage exit(3) calling exit is not thread-safe. And with glibc 2.28 (and probably also with glibc >=2.27) sometimes child processes created in fork_thread can get stuck on process exit in glibc's __run_exit_handlers trying to acquire some lock which was in locked state while the fork was created. This can happen when exit is called in mmap_thread concurrently to the fork. While the main process will still return with PASSED some of its children are left behind. Comparing the source code with the original program as described in the commit 2b7e8665b4ff51c034c55df3cff76518d1a9ee3a of linux kernel >=4.13 the exits in mmap_thread and fork_thread should not be necessary to trigger the original bug. Therefore those exit calls are removed. The mmap_thread and fork_thread should still exit when their corresponding main thread in do_test_fork calls exit_group. The remaining exit in do_test_fork will be called in the main thread without any concurrent thread in the same process. Signed-off-by: Mathias Fiedler Acked-by: Cyril Hrubis Acked-by: Jan Stancek --- testcases/cve/cve-2017-17052.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/testcases/cve/cve-2017-17052.c b/testcases/cve/cve-2017-17052.c index d2452007196..81123fce8b4 100644 --- a/testcases/cve/cve-2017-17052.c +++ b/testcases/cve/cve-2017-17052.c @@ -46,8 +46,6 @@ static void *mmap_thread(void *arg) for (;;) { SAFE_MMAP(NULL, 0x1000000, PROT_READ, MAP_POPULATE|MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); - if (*do_exit) - exit(0); } return arg; @@ -55,9 +53,6 @@ static void *mmap_thread(void *arg) static void *fork_thread(void *arg) { - if (*do_exit) - exit(0); - usleep(rand() % 10000); SAFE_FORK();