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Mon, 16 Mar 2026 07:52:01 -0400 X-MC-Unique: Esin8boYNg2gUyOr0f2cXA-1 X-Mimecast-MFC-AGG-ID: Esin8boYNg2gUyOr0f2cXA_1773661918 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 41DAA1884EC3; Mon, 16 Mar 2026 11:51:38 +0000 (UTC) Received: from fedora (unknown [10.45.225.204]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id C67D930002DC; Mon, 16 Mar 2026 11:51:27 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 16 Mar 2026 12:51:36 +0100 (CET) Date: Mon, 16 Mar 2026 12:51:26 +0100 From: Oleg Nesterov To: Deepanshu Kartikey Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kees@kernel.org, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, brauner@kernel.org, dietmar.eggemann@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzbot+bbe6b99feefc3a0842de@syzkaller.appspotmail.com Subject: Re: [PATCH v2] kernel/fork: validate exit_signal in kernel_clone() Message-ID: References: <20260316104536.558108-1-kartikey406@gmail.com> MIME-Version: 1.0 In-Reply-To: <20260316104536.558108-1-kartikey406@gmail.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: iXKe_tCRc3la7wtunj8guclWrjYRvBCzAdBheJJ00rU_1773661918 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Stat-Signature: xidpshrnoyw35tuezosspxyr14rwh1b7 X-Rspam-User: X-Rspamd-Queue-Id: 996D420007 X-Rspamd-Server: rspam12 X-HE-Tag: 1773661927-161408 X-HE-Meta: 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 gjWjSABG ungz4vFNdW7HdQeFJHsA168KiYTJAlTA/wqYrfOIKUAYuqjuUbXRiKgTYgymVCtqB0ios6Z2xRoxdPIDY6Jg6iDmdTi9NmJ7wcfDCjjKmdGoJM1M9B/e5Jlon1mcS37MjRXFSKPa04fDMcqre8q66/7NkjckUnpWY/rh/yIjtG8b7peAqWYl/e7k/W1WqdegbT/IH+UQrf+jW1x8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Deepanshu, Let me repeat, the changelog should be updated. On 03/16, Deepanshu Kartikey wrote: > > CSIGNAL is 0xff, so values in the range 65-255 are possible. However, > valid_signal() only accepts signals up to _NSIG (64 on x86_64), causing > a WARN_ON in do_notify_parent() when the process exits: > > WARNING: kernel/signal.c:2174 do_notify_parent+0xc7e/0xd70 Again, do_notify_parent-sanitize-the-valid_signal-checks.patch was dropped. do_notify_parent() won't WARN() in this case. > Note that this is a user-visible change: previously, passing an invalid > exit_signal to clone() was silently accepted. The man page for clone() > does not document any defined behavior for invalid exit_signal values, > so rejecting them with -EINVAL is the correct behavior. It is unlikely > that any sane application relies on passing an invalid exit_signal. Yes, it only documents that if exit_signal == 0 then the parent process is not signaled when the child terminates. But in fact a non-zero non-valid signal acts the same way. > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -2687,6 +2687,8 @@ pid_t kernel_clone(struct kernel_clone_args *args) > (args->pidfd == args->parent_tid)) > return -EINVAL; > > + if (!valid_signal(args->exit_signal)) > + return -EINVAL; OK, but then it also makes sense to remove the same valid_signal() check in copy_clone_args_from_user() ? Oleg.