linux-kernel - [PATCH] Fixing warning of directly dereferencing _

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20231025222811.855336-1-singhabhinav9051571833@gmail.com>
Date:   Thu, 26 Oct 2023 03:58:11 +0530
From:   Abhinav Singh <singhabhinav9051571833@...il.com>
To:     akpm@...ux-foundation.org, brauner@...nel.org, surenb@...gle.com,
        mst@...hat.com, michael.christie@...cle.com,
        mathieu.desnoyers@...icios.com, mjguzik@...il.com,
        npiggin@...il.com, shakeelb@...gle.com, peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Abhinav Singh <singhabhinav9051571833@...il.com>
Subject: [PATCH] Fixing warning of directly dereferencing  __rcu tagged

This patch fixes the warning about directly dereferencing a pointer
tagged with __rcu annotation.

Dereferencing the pointers tagged with __rcu directly should 
always be avoided according to the docs. There is a rcu helper 
functions rcu_dereference(...) to use when dereferencing a __rcu 
pointer. This functions returns the non __rcu tagged pointer. 
Like normal pointer there should be a check for null case when 
further dereferencing the returned dereferenced __rcu pointer.


Signed-off-by: Abhinav Singh <singhabhinav9051571833@...il.com>
---
 kernel/fork.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 10917c3e1f03..5afb1b389a66 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2369,7 +2369,9 @@ __latent_entropy struct task_struct *copy_process(
 
 	retval = -EAGAIN;
 	if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
-		if (p->real_cred->user != INIT_USER &&
+		const struct cred *real_cred = rcu_dereference(p->real_cred);
+
+		if (real_cred && real_cred->user != INIT_USER &&
 		    !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
 			goto bad_fork_cleanup_count;
 	}
-- 
2.39.2