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Thu, 04 Dec 2025 06:41:50 -0800 (PST) Received: from eclypsium-Latitude-5490.arg.eclypsium.com ([190.123.123.8]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-bf748c6bcacsm1831432a12.0.2025.12.04.06.41.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Dec 2025 06:41:49 -0800 (PST) From: ellyndra To: linux-kernel@vger.kernel.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com Cc: Elly I Esparza Subject: [PATCH RESEND] kprobes: Blacklist risky functions from being probed Date: Thu, 4 Dec 2025 11:41:41 -0300 Message-ID: <20251204144142.61936-1-ellyesparza8@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Elly I Esparza Blacklist 'x64_sys_call()' from being kprobed to prevent syscall hooking techniques that overwrite the content of a 'case' block inside the main syscall dispatch switch statement. Also blacklist 'kallsyms_lookup_name()' to prevent a potential bypass of the blacklist, since this function can be used to discover and target arbitrary kernel symbols. Add a Kconfig option under security/ to enable or disable this feature. Signed-off-by: Elly I Esparza --- This repo shows how kprobes without this blacklist entries could be exploited: https://github.com/1337-42/FlipSwitch-dev/ --- arch/x86/entry/syscall_64.c | 9 ++++++++- kernel/kallsyms.c | 3 +++ security/Kconfig | 8 ++++++++ 3 files changed, 19 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c index b6e68ea98b83..e878fa865532 100644 --- a/arch/x86/entry/syscall_64.c +++ b/arch/x86/entry/syscall_64.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0-only /* 64-bit system call dispatch */ =20 +#include #include #include #include @@ -39,6 +40,9 @@ long x64_sys_call(const struct pt_regs *regs, unsigned in= t nr) default: return __x64_sys_ni_syscall(regs); } } +#ifdef CONFIG_SEC_KPROBES +NOKPROBE_SYMBOL(x64_sys_call) +#endif =20 #ifdef CONFIG_X86_X32_ABI long x32_sys_call(const struct pt_regs *regs, unsigned int nr) @@ -48,7 +52,10 @@ long x32_sys_call(const struct pt_regs *regs, unsigned i= nt nr) default: return __x64_sys_ni_syscall(regs); } } -#endif +#ifdef CONFIG_SEC_KPROBES +NOKPROBE_SYMBOL(x32_sys_call) +#endif //CONFIG_SEC_KPROBES +#endif //CONFIG_X86_X32_ABI =20 static __always_inline bool do_syscall_x64(struct pt_regs *regs, int nr) { diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 1e7635864124..4082e98681a4 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -234,6 +234,9 @@ unsigned long kallsyms_lookup_name(const char *name) =20 return module_kallsyms_lookup_name(name); } +#ifdef CONFIG_SEC_KPROBES +NOKPROBE_SYMBOL(kallsyms_lookup_name) +#endif =20 /* * Iterate over all symbols in vmlinux. For symbols from modules use diff --git a/security/Kconfig b/security/Kconfig index 285f284dfcac..a0906a5a7410 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -286,5 +286,13 @@ config LSM =20 source "security/Kconfig.hardening" =20 +config SEC_KPROBES + bool "Secure kprobe blacklist" + depends on KPROBES + help + Adds functions x64_syscall_table() and kallsyms_lookup_name() + to the kprobe blacklist to prevent syscall hooking attacks. + If in doubt, say "N". + endmenu =20 --=20 2.43.0