linux-kernel - [PATCH] posix-timers: Plug a potential memory leak

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Message-ID: <87zf8obv45.ffs@tglx>
Date: Fri, 14 Nov 2025 14:29:30 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: syzbot <syzbot+9c47ad18f978d4394986@...kaller.appspotmail.com>,
 anna-maria@...utronix.de, frederic@...nel.org,
 linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [PATCH] posix-timers: Plug a potential memory leak

When posix timer creation is set to allocate a given timer ID and the
access to the user space value faults, the function terminates without
freeing the already allocated posix timer structure.

Move the allocation after the user space access to cure that.

Fixes: ec2d0c04624b ("posix-timers: Provide a mechanism to allocate a given timer ID")
Reported-by: syzbot+9c47ad18f978d4394986@...kaller.appspotmail.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Closes: https://lore.kernel.org/all/69155df4.a70a0220.3124cb.0017.GAE@google.com
---
 kernel/time/posix-timers.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -475,12 +475,6 @@ static int do_timer_create(clockid_t whi
 	if (!kc->timer_create)
 		return -EOPNOTSUPP;
 
-	new_timer = alloc_posix_timer();
-	if (unlikely(!new_timer))
-		return -EAGAIN;
-
-	spin_lock_init(&new_timer->it_lock);
-
 	/* Special case for CRIU to restore timers with a given timer ID. */
 	if (unlikely(current->signal->timer_create_restore_ids)) {
 		if (copy_from_user(&req_id, created_timer_id, sizeof(req_id)))
@@ -490,6 +484,12 @@ static int do_timer_create(clockid_t whi
 			return -EINVAL;
 	}
 
+	new_timer = alloc_posix_timer();
+	if (unlikely(!new_timer))
+		return -EAGAIN;
+
+	spin_lock_init(&new_timer->it_lock);
+
 	/*
 	 * Add the timer to the hash table. The timer is not yet valid
 	 * after insertion, but has a unique ID allocated.