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

From: Alexey Gladkov <[email-masked]>
Date: Wed, 12 Jan 2022 15:28:46 +0100

On Wed, Jan 12, 2022 at 03:14:45PM +0100, Alexey Gladkov wrote:
> 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.

It should be fixed in the four places:

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 22070f004e97..5c373a453f43 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;
@@ -292,7 +292,7 @@ static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts,
 {
 	struct ucounts *iter, *next;
 	for (iter = ucounts; iter != last; iter = next) {
-		long dec = atomic_long_sub_return(1, &iter->ucount[type]);
+		long dec = atomic_long_sub_return(1, &iter->rlimit[type]);
 		WARN_ON_ONCE(dec < 0);
 		next = iter->ns->ucounts;
 		if (dec == 0)
@@ -313,7 +313,7 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type)
 	long dec, ret = 0;
 
 	for (iter = ucounts; iter; iter = iter->ns->ucounts) {
-		long new = atomic_long_add_return(1, &iter->ucount[type]);
+		long new = atomic_long_add_return(1, &iter->rlimit[type]);
 		if (new < 0 || new > max)
 			goto unwind;
 		if (iter == ucounts)
@@ -330,7 +330,7 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type)
 	}
 	return ret;
 dec_unwind:
-	dec = atomic_long_sub_return(1, &iter->ucount[type]);
+	dec = atomic_long_sub_return(1, &iter->rlimit[type]);
 	WARN_ON_ONCE(dec < 0);
 unwind:
 	do_dec_rlimit_put_ucounts(ucounts, iter, type);

-- 
Rgrds, legion