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Message-Id: <54b0cf752c2c275a164aa980e2d8e4e464797ca1.1610299858.git.gladkov.alexey@gmail.com>
Date: Sun, 10 Jan 2021 18:33:47 +0100
From: Alexey Gladkov <gladkov.alexey@...il.com>
To: LKML <linux-kernel@...r.kernel.org>,
Linux Containers <containers@...ts.linux-foundation.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>
Cc: Alexey Gladkov <legion@...nel.org>,
"Eric W . Biederman" <ebiederm@...ssion.com>,
Kees Cook <keescook@...omium.org>,
Christian Brauner <christian@...uner.io>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [RFC PATCH v2 8/8] Move RLIMIT_NPROC check to the place where we increment the counter
After calling set_user(), we always have to call commit_creds() to apply
new credentials upon the current task. There is no need to separate
limit check and counter incrementing.
Signed-off-by: Alexey Gladkov <gladkov.alexey@...il.com>
---
kernel/cred.c | 22 +++++++++++++++++-----
kernel/sys.c | 13 -------------
2 files changed, 17 insertions(+), 18 deletions(-)
diff --git a/kernel/cred.c b/kernel/cred.c
index 89a945571533..770447b4f4de 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -488,14 +488,26 @@ int commit_creds(struct cred *new)
if (!gid_eq(new->fsgid, old->fsgid))
key_fsgid_changed(new);
- /* do it
- * RLIMIT_NPROC limits on user->processes have already been checked
- * in set_user().
- */
alter_cred_subscribers(new, 2);
if (new->user != old->user || new->user_ns != old->user_ns) {
+ bool overlimit;
+
set_cred_ucounts(new, new->user_ns, new->euid);
- inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1);
+
+ overlimit = inc_rlimit_ucounts_and_test(new->ucounts, UCOUNT_RLIMIT_NPROC,
+ 1, rlimit(RLIMIT_NPROC));
+
+ /*
+ * We don't fail in case of NPROC limit excess here because too many
+ * poorly written programs don't check set*uid() return code, assuming
+ * it never fails if called by root. We may still enforce NPROC limit
+ * for programs doing set*uid()+execve() by harmlessly deferring the
+ * failure to the execve() stage.
+ */
+ if (overlimit && new->user != INIT_USER)
+ current->flags |= PF_NPROC_EXCEEDED;
+ else
+ current->flags &= ~PF_NPROC_EXCEEDED;
}
rcu_assign_pointer(task->real_cred, new);
rcu_assign_pointer(task->cred, new);
diff --git a/kernel/sys.c b/kernel/sys.c
index c2734ab9474e..180c4e06064f 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -467,19 +467,6 @@ static int set_user(struct cred *new)
if (!new_user)
return -EAGAIN;
- /*
- * We don't fail in case of NPROC limit excess here because too many
- * poorly written programs don't check set*uid() return code, assuming
- * it never fails if called by root. We may still enforce NPROC limit
- * for programs doing set*uid()+execve() by harmlessly deferring the
- * failure to the execve() stage.
- */
- if (is_ucounts_overlimit(new->ucounts, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC)) &&
- new_user != INIT_USER)
- current->flags |= PF_NPROC_EXCEEDED;
- else
- current->flags &= ~PF_NPROC_EXCEEDED;
-
free_uid(new->user);
new->user = new_user;
return 0;
--
2.29.2
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