Hi, When I'm testing Glibc master branch for upcoming 2.39 release, I noticed an alarming test failure on mips64el: FAIL: stdlib/tst-arc4random-thread I've gathered some info about it and pasted my findings into https://sourceware.org/glibc/wiki/Testing/Tests/stdlib/tst-arc4random-thread. Finally I was able to reduce the test case into: #include <stdlib.h> #include <errno.h> #include <pthread.h> #include <unistd.h> #include <fcntl.h> void * test_thread (void *) { char buf[16] = {}; int fd = open("/dev/zero", O_RDONLY); while (1) { ssize_t ret = read (fd, buf, 7); if (ret == -1 && errno == EFAULT) abort (); } } void * fork_thread (void *) { while (1) { if (!fork ()) _exit (0); } } int main (void) { pthread_t test_th; pthread_t fork_th; pthread_create (&test_th, NULL, test_thread, NULL); pthread_create (&fork_th, NULL, fork_thread, NULL); pthread_join (test_th, NULL); pthread_join (fork_th, NULL); } When running this on the mainline kernel (revision 6.8.0-rc1+- g7ed2632ec7d72e926b9e8bcc9ad1bb0cd37274bf) it fails in milliseconds. Some "interesting" aspects: 1. This is related to the size parameter passed to read (). When it's less than 8 it fails, but when it's 8 or greater there is no failure. 2. This is not related to if "buf" is initialized or not. Now I'm suspecting this might be a kernel bug. Any pointer to further triage? -- Xi Ruoyao <xry111@xxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
