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

From: Alexey Gladkov <[email-masked]>
Date: Wed, 12 Jan 2022 15:14:45 +0100

On Wed, Jan 12, 2022 at 03:02:54PM +0100, Christian Brauner wrote:
> On Wed, Jan 12, 2022 at 02:22:42PM +0100, Anders Roxell wrote:
> > On Wed, 12 Jan 2022 at 14:18, Christian Brauner
> > <[email-masked]> wrote:
> > >
> > > 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.
> > 
> > I did a git bisect and that pointed me to this patch too.
> 
> Uhm, doesn't this want to be:

Yes. I miss it. I tried not to mix the logic, but I myself stepped on this
problem.

> 
> diff --git a/kernel/ucount.c b/kernel/ucount.c
> index 22070f004e97..108c6a879cd8 100644
> --- a/kernel/ucount.c
> +++ b/kernel/ucount.c
> @@ -264,7 +264,7 @@ long inc_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v)
>         long ret = 0;
> 
>         for (iter = ucounts; iter; iter = iter->ns->ucounts) {
> -               long new = atomic_long_add_return(v, &iter->ucount[type]);
> +               long new = atomic_long_add_return(v, &iter->rlimit[type]);
>                 if (new < 0 || new > max)
>                         ret = LONG_MAX;
>                 else if (iter == ucounts)
> @@ -279,7 +279,7 @@ bool dec_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v)
>         struct ucounts *iter;
>         long new = -1; /* Silence compiler warning */
>         for (iter = ucounts; iter; iter = iter->ns->ucounts) {
> -               long dec = atomic_long_sub_return(v, &iter->ucount[type]);
> +               long dec = atomic_long_sub_return(v, &iter->rlimit[type]);
>                 WARN_ON_ONCE(dec < 0);
>                 if (iter == ucounts)
>                         new = dec;
> 
> 
> otherwise,
> 
> inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_NPROC, 1)
> 
> means
> 
> long inc_rlimit_ucounts(struct ucounts *ucounts, UCOUNT_RLIMIT_NPROC, long v)
> {
> 	struct ucounts *iter;
> 	long max = LONG_MAX;
> 	long ret = 0;
> 
> 	for (iter = ucounts; iter; iter = iter->ns->ucounts) {
> 		long new = atomic_long_add_return(v, &iter->ucount[UCOUNT_RLIMIT_NPROC]);
> 		if (new < 0 || new > max)
> 			ret = LONG_MAX;
> 		else if (iter == ucounts)
> 			ret = new;
> 		max = get_userns_rlimit_max(iter->ns, UCOUNT_RLIMIT_NPROC);
> 	}
> 	return ret;
> }
> 
> which means that UCOUNT_RLIMIT_NPROC overwrites ucount[UCOUNT_RLIMIT_NPROC]?
> 

-- 
Rgrds, legion