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- From a8bc44936202692edcd82a48c07d7cf27d6ed8ee Mon Sep 17 00:00:00 2001
- From: Hongxu Jia <hongxu.jia@windriver.com>
- Date: Sun, 29 Aug 2021 20:49:16 +0800
- Subject: [PATCH] fix create thread failed in unprivileged process [BZ #28287]
- Since commit [d8ea0d0168 Add an internal wrapper for clone, clone2 and clone3]
- applied, start a unprivileged container (docker run without --privileged),
- it creates a thread failed in container.
- In commit d8ea0d0168, it calls __clone3 if HAVE_CLONE3_WAPPER is defined. If
- __clone3 returns -1 with ENOSYS, fall back to clone or clone2.
- As known from [1], cloneXXX fails with EPERM if CLONE_NEWCGROUP,
- CLONE_NEWIPC, CLONE_NEWNET, CLONE_NEWNS, CLONE_NEWPID, or CLONE_NEWUTS
- was specified by an unprivileged process (process without CAP_SYS_ADMIN)
- [1] https://man7.org/linux/man-pages/man2/clone3.2.html
- So if __clone3 returns -1 with EPERM, fall back to clone or clone2 could
- fix the issue. Here are the test steps:
- 1) Prepare test code
- cat > conftest.c <<ENDOF
- #include <pthread.h>
- #include <stdio.h>
- int check_me = 0;
- void* func(void* data) {check_me = 42; printf("start thread: check_me %d\n", check_me); return &check_me;}
- int main()
- {
- pthread_t t;
- void *ret;
- pthread_create (&t, 0, func, 0);
- pthread_join (t, &ret);
- printf("check_me %d, p %p\n", check_me, &ret);
- return (check_me != 42 || ret != &check_me);
- }
- ENDOF
- 2) Compile
- gcc -o conftest -pthread conftest.c
- 3) Start a container with glibc 2.34 installed
- [skip details]
- docker run -it <container-image-name> bash
- 4) Run conftest without this patch
- $ ./conftest
- check_me 0, p 0x7ffd91ccd400
- 5) Run conftest with this patch
- $ ./conftest
- start thread: check_me 42
- check_me 42, p 0x7ffe253c6f20
- Upstream-Status: Submitted [libc-alpha@sourceware.org]
- Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
- ---
- sysdeps/unix/sysv/linux/clone-internal.c | 2 +-
- 1 file changed, 1 insertion(+), 1 deletion(-)
- diff --git a/sysdeps/unix/sysv/linux/clone-internal.c b/sysdeps/unix/sysv/linux/clone-internal.c
- index 979f7880be..97101994e8 100644
- --- a/sysdeps/unix/sysv/linux/clone-internal.c
- +++ b/sysdeps/unix/sysv/linux/clone-internal.c
- @@ -52,7 +52,7 @@ __clone_internal (struct clone_args *cl_args,
- /* Try clone3 first. */
- int saved_errno = errno;
- ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
- - if (ret != -1 || errno != ENOSYS)
- + if (ret != -1 || (errno != ENOSYS && errno != EPERM))
- return ret;
-
- /* NB: Restore errno since errno may be checked against non-zero
- --
- 2.30.2
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