Subject: Re: [next]: LTP: getxattr05.c:97: TFAIL: unshare(CLONE_NEWUSER) failed: ENOSPC (28)

From: Christian Brauner <[email-masked]>
Date: Wed, 12 Jan 2022 14:18:37 +0100

On Wed, Jan 12, 2022 at 05:15:37PM +0530, Naresh Kamboju wrote:
> While testing LTP syscalls with Linux next 20220110 (and till date 20220112)
> on x86_64, i386, arm and arm64 the following tests failed.
> 
> tst_test.c:1365: TINFO: Timeout per run is 0h 15m 00s
> getxattr05.c:87: TPASS: Got same data when acquiring the value of
> system.posix_acl_access twice
> getxattr05.c:97: TFAIL: unshare(CLONE_NEWUSER) failed: ENOSPC (28)
> tst_test.c:391: TBROK: Invalid child (13545) exit value 1
> 
> fanotify17.c:176: TINFO: Test #1: Global groups limit in privileged user ns
> fanotify17.c:155: TFAIL: unshare(CLONE_NEWUSER) failed: ENOSPC (28)
> tst_test.c:391: TBROK: Invalid child (14739) exit value 1
> 
> sendto03.c:48: TBROK: unshare(268435456) failed: ENOSPC (28)
> 
> setsockopt05.c:45: TBROK: unshare(268435456) failed: ENOSPC (28)
> 
> strace output:
> --------------
> [pid   481] wait4(-1, 0x7fff52f5ae8c, 0, NULL) = -1 ECHILD (No child processes)
> [pid   481] clone(child_stack=NULL,
> flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
> child_tidptr=0x7f3af0fa7a10) = 483
> strace: Process 483 attached
> [pid   481] wait4(-1,  <unfinished ...>
> [pid   483] unshare(CLONE_NEWUSER)      = -1 ENOSPC (No space left on device)

This looks like another regression in the ucount code. Reverting the
following commit fixes it and makes the getxattr05 test work again:

commit 0315b634f933b0f12cfa82660322f6186c1aa0f4
Author: Alexey Gladkov <[email-masked]>
Date:   Fri Dec 17 15:48:23 2021 +0100

    ucounts: Split rlimit and ucount values and max values

    Since the semantics of maximum rlimit values are different, it would be
    better not to mix ucount and rlimit values. This will prevent the error
    of using inc_count/dec_ucount for rlimit parameters.

    This patch also renames the functions to emphasize the lack of
    connection between rlimit and ucount.

    v2:
    - Fix the array-index-out-of-bounds that was found by the lkp project.

    Reported-by: kernel test robot <[email-masked]>
    Signed-off-by: Alexey Gladkov <[email-masked]>
    Link: https://lkml.kernel.org/r/[email-masked]
    Signed-off-by: Eric W. Biederman <[email-masked]>

The issue only surfaces if /proc/sys/user/max_user_namespaces is
actually written to.