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[122.63.67.56]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2cad6f260acsm8227305ad.6.2026.07.03.04.26.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jul 2026 04:27:00 -0700 (PDT) From: Tao Liu To: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, bhe@redhat.com, zohar@linux.ibm.com, roberto.sassu@huawei.com, dmitry.kasatkin@gmail.com, eric.snowberg@oracle.com, linux-integrity@vger.kernel.org, pratyush@kernel.org, Markus.Elfring@web.de, kernel-janitors@vger.kernel.org, jarkko@kernel.org, Tao Liu , stable@vger.kernel.org, Nutty Liu Subject: [PATCH v4] riscv: Prevent NULL pointer dereference in machine_kexec_prepare Date: Fri, 3 Jul 2026 23:15:31 +1200 Message-ID: <20260703111530.91285-2-ltao@redhat.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A NULL pointer dereference issue is noticed in riscv's machine_kexec_prepare(), where image->segment[i].buf might be NULL and copied unchecked. The NULL buf comes from ima_add_kexec_buffer(), where kbuf is added by kexec_add_buffer(), but kbuf.buffer is NULL, then it is copied without a check in machine_kexec_prepare(). Relevant path: kexec_file_load -> kimage_file_alloc_init() -> kimage_file_prepare_segments() -> ima_add_kexec_buffer() -> kexec_add_buffer() -> machine_kexec_prepare() -> memcpy() Address this by adding a check before the data copy attempt. Fixes: b7fb4d78a6ad ("RISC-V: use memcpy for kexec_file mode") Cc: stable@vger.kernel.org Closes: https://lore.kernel.org/kexec/CAO7dBbVftLUhd2qrh7hmijTB3PEPfZAhykCGqEfrPoOcSrrj-w@mail.gmail.com/ Acked-by: Baoquan He Acked-by: Pratyush Yadav Reviewed-by: Nutty Liu Signed-off-by: Tao Liu --- v4 -> v3: 1) Remove code comment. 2) Replace (buf == NULL) to (!buf). 3) Reword commit message. link to v1: https://lore.kernel.org/linux-riscv/20260529032739.13264-2-ltao@redhat.com/ link to v2: https://lore.kernel.org/linux-riscv/20260627222602.23594-2-ltao@redhat.com/ link to v3: https://lore.kernel.org/linux-riscv/20260701025732.66330-2-ltao@redhat.com/ --- arch/riscv/kernel/machine_kexec.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c index 2306ce3e5f22..738df176ff6f 100644 --- a/arch/riscv/kernel/machine_kexec.c +++ b/arch/riscv/kernel/machine_kexec.c @@ -41,6 +41,9 @@ machine_kexec_prepare(struct kimage *image) if (image->segment[i].memsz <= sizeof(fdt)) continue; + if (!image->segment[i].buf) + continue; + if (image->file_mode) memcpy(&fdt, image->segment[i].buf, sizeof(fdt)); else if (copy_from_user(&fdt, image->segment[i].buf, sizeof(fdt))) -- 2.54.0