Date: Mon, 22 May 2017 20:21:57 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 219464] [PATCH] linux_getrandom always returns 0 Message-ID: <bug-219464-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219464 Bug ID: 219464 Summary: [PATCH] linux_getrandom always returns 0 Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Keywords: patch Severity: Affects Some People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: maciej@pasternacki.net Created attachment 182818 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=182818&action=edit linux_getrandom.patch In a Linux-based jail, running Ubuntu 16.04, `lsb_release` command (which is widely used in various scripts and during Factorio startup) hangs. `top` shows it forks a `python3.5` process which uses 100% CPU. `truss` shows this process repeatedly calls `linux_getrandom(…)`, which always returns 0. `man 2 getrandom` on Ubuntu 16.04 specifies that this syscall should return number of random bytes written (http://man7.org/linux/man-pages/man2/getrandom.2.html). A short test program shows that this it returns positive value on Linux, and returns 0 on FreeBSD despite the fact that random bytes have been written to the buffer: > $ cat test_getrandom.c > #define _GNU_SOURCE > #include <unistd.h> > #include <sys/syscall.h> > #include <stdio.h> > #include <linux/random.h> > > int main(void) { > int rv; > int buf = 0; > rv = syscall(SYS_getrandom, &buf, sizeof(buf), GRND_NONBLOCK); > printf("getrandom(&buf, %d, 0) => %d buf=%d\n", (int)sizeof(buf), rv, buf); > return 0; > } When this program runs natively on Linux, `getrandom(2)` returns size of buffer: > $ ./test_getrandom > getrandom(&buf, 4, 0) => 4 buf=-707083248 On FreeBSD 12-CURRENT (possibly also on 11-STABLE, r315505 which introduces this implementation is marked for MFC after 1 month), the syscall always returns 0: > $ ./test_getrandom > getrandom(&buf, 4, 0) => 0 buf=-1643413282 After applying attached patch, return value reported from the test program is the same as on native Linux, and `lsb_release` no longer hangs: > $ ./test_getrandom > getrandom(&buf, 4, 0) => 4 buf=-943351330 > $ lsb_release -a > No LSB modules are available. > Distributor ID: Ubuntu > Description: Ubuntu 16.04.2 LTS > Release: 16.04 > Codename: xenial -- You are receiving this mail because: You are the assignee for the bug.
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