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([2405:201:682f:389d:4191:5f1c:7dc6:bad2]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c739dfbf4fesm3507947a12.0.2026.03.06.22.42.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Mar 2026 22:42:14 -0800 (PST) From: Deepanshu Kartikey To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kees@kernel.org, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, brauner@kernel.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Deepanshu Kartikey , syzbot+bbe6b99feefc3a0842de@syzkaller.appspotmail.com, Deepanshu Kartikey Subject: [PATCH] kernel/fork: validate exit_signal in clone() syscall Date: Sat, 7 Mar 2026 12:12:02 +0530 Message-ID: <20260307064202.353405-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: D9317160002 X-Stat-Signature: 8yxjsax7ycn9bqa9hzstadu9wn7dghtx X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1772865736-869026 X-HE-Meta: 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 QYKqiJ1J 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When a child process exits, it sends exit_signal to its parent via do_notify_parent(). The clone() syscall constructs exit_signal as: (lower_32_bits(clone_flags) & CSIGNAL) 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 The syzkaller reproducer triggers this by calling clone() with flags=0x80, resulting in exit_signal = (0x80 & CSIGNAL) = 128, which exceeds _NSIG and is not a valid signal. The comment above kernel_clone() states that callers are expected to validate exit_signal. clone3() correctly does this: if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) || !valid_signal(args.exit_signal))) return -EINVAL; The clone() syscall has no such check. Add the missing valid_signal() check to clone(), consistent with the existing validation in clone3(). Fixes: 3f2c788a1314 ("fork: prevent accidental access to clone3 features") Reported-by: syzbot+bbe6b99feefc3a0842de@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=bbe6b99feefc3a0842de Tested-by: syzbot+bbe6b99feefc3a0842de@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey --- kernel/fork.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/fork.c b/kernel/fork.c index 947a8dbce06a..dbe26ac6ca10 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2845,7 +2845,8 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, .stack = newsp, .tls = tls, }; - + if (!valid_signal(args.exit_signal)) + return -EINVAL; return kernel_clone(&args); } #endif -- 2.43.0