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imf30.hostedemail.com; none Received: from omf10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 159DB57397; Thu, 18 Sep 2025 15:29:19 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf10.hostedemail.com (Postfix) with ESMTPA id 8923330; Thu, 18 Sep 2025 15:29:14 +0000 (UTC) Date: Thu, 18 Sep 2025 11:30:22 -0400 From: Steven Rostedt To: Sebastian Andrzej Siewior Cc: Vlastimil Babka , Thomas Gleixner , Peter Zijlstra , syzbot , Liam.Howlett@oracle.com, akpm@linux-foundation.org, bsegall@google.com, david@redhat.com, dietmar.eggemann@arm.com, juri.lelli@redhat.com, kees@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mgorman@suse.de, mhocko@suse.com, mingo@redhat.com, rppt@kernel.org, surenb@google.com, syzkaller-bugs@googlegroups.com, vincent.guittot@linaro.org, vschneid@redhat.com Subject: Re: [PATCH] futex: Use correct exit on failure from futex_hash_allocate_default() Message-ID: <20250918113022.1b97d977@gandalf.local.home> In-Reply-To: <20250918130945.-7SIRk8Z@linutronix.de> References: <68cb1cbd.050a0220.2ff435.0599.GAE@google.com> <867144d3-b05e-4ce2-8bb6-da01e10fbd73@suse.cz> <20250918130945.-7SIRk8Z@linutronix.de> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+TTPLGd6WX6aq3rap/uZBpfrnji4VecK0= X-HE-Meta: U2FsdGVkX1/urWqjcd2GFQknJ54dZpoXNJwoQqbuoC0perxLalFSrYy7kgiLvkmLA8YVWi6aGxg4bBNLTzGZ8BkLZKhgn9VtkWHRwcN81nmT7hUTth99wPdPbHq7dUSpNOz+uBYU2BNyfLKGy1dXqjXZOEVcOyod3Tr3ctFjSjm3MW3hmYF5b+bl4i5c0vn9qdPhJKlKV2i0Ye/HVqkXMEOf66vD1KSjP8pdk4bbLvaVSpLGYPTmtofZnOoGL+yjgmBQznEKfyXoRbdo9ewufM62EB/SNVcAYkZnlp3lEgQAkB0JHKhXkJu/EtzJc187JPtT99aGZfZ8/EgOZVKW3odD+3YZZo2ZFvlrRcPHinZFtq/qKaBaW7r5dgdn4v7AV9j9nqKyiVpRW5LhzEibPOnyGCg/Va5B0PpgX//V24mdY22wZpJiDkhxalHzhvS2JJ+qs9MiKKSt8xQDs0kDWGDyLzEjOZJPumDQxRLTGbw= X-Stat-Signature: 5k3m8kciftd13nqeeizubc5uj35nansc X-Rspam-User: X-Rspamd-Queue-Id: 5484D8000D X-Rspamd-Server: rspam10 X-HE-Tag-Orig: 1758209354-859747 X-HE-Tag: 1758209361-194479 X-HE-Meta: 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 /j/KCaQI xS2pYYoq9CkldHbHLeGyLON7LgiOmod9SzXuEUEOYiP2RltDrA1gIv467LMSHko34S/Axh6YmYGdUYzdJoO+iVenbLGvDQHAZ1lVqfq3ND+F+2j2sUKOeP9kDJcRRdqQwNaRRC5PeXAkQx3kL/xb9UitXMJEucn61a1NcjkkwgJZzt1pgntnVGrb4bKNQv1QeZtO+hY7ovKyLpSU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 18 Sep 2025 15:09:45 +0200 Sebastian Andrzej Siewior wrote: > copy_process() uses the wrong error exit path from > futex_hash_allocate_default(). > After exiting from futex_hash_allocate_default(), neither tasklist_lock > nor siglock has been acquired. The exit label bad_fork_core_free unlocks > both of these locks which is wrong. > > The previous label, bad_fork_cancel_cgroup, is the correct exit. > sched_cgroup_fork() did not allocate any resources that need to freed. > > Use bad_fork_cancel_cgroup on error exit from > futex_hash_allocate_default(). if (need_futex_hash_allocate_default(clone_flags)) { retval = futex_hash_allocate_default(); if (retval) goto bad_fork_core_free; [..] } [..] write_lock_irq(&tasklist_lock); [..] klp_copy_process(p); sched_core_fork(p); spin_lock(¤t->sighand->siglock); [..] bad_fork_core_free: sched_core_free(p); spin_unlock(¤t->sighand->siglock); write_unlock_irq(&tasklist_lock); bad_fork_cancel_cgroup: cgroup_cancel_fork(p, args); Yep, looks bad to me! Reviewed-by: Steven Rostedt (Google) -- Steve > > Fixes: 7c4f75a21f636 ("futex: Allow automatic allocation of process wide futex hash") > Reported-by: syzbot+80cb3cc5c14fad191a10@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/68cb1cbd.050a0220.2ff435.0599.GAE@google.com > Signed-off-by: Sebastian Andrzej Siewior >