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Wed, 15 Jan 2025 22:58:32 -0800 (PST) X-Google-Smtp-Source: AGHT+IEZwFoiLlhavnDUatbgb2kTU1Y2y/dIgU8v9im+rqhrRya3h6VZuF6F+cRCzUWzSL0lLNhCmw== X-Received: by 2002:a17:90b:51c8:b0:2f4:4003:f3d4 with SMTP id 98e67ed59e1d1-2f548f5f883mr45301018a91.30.1737010712075; Wed, 15 Jan 2025 22:58:32 -0800 (PST) Received: from localhost ([43.228.180.230]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2f72c2bae59sm2754048a91.30.2025.01.15.22.58.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2025 22:58:31 -0800 (PST) From: Coiby Xu To: kexec@lists.infradead.org Cc: Ondrej Kozina , Milan Broz , Thomas Staudt , =?UTF-8?q?Daniel=20P=20=2E=20Berrang=C3=A9?= , Kairui Song , Jan Pazdziora , Pingfan Liu , Baoquan He , Dave Young , linux-kernel@vger.kernel.org, x86@kernel.org, Dave Hansen , Vitaly Kuznetsov , Eric Biederman Subject: [PATCH v7 1/7] kexec_file: allow to place kexec_buf randomly Date: Thu, 16 Jan 2025 14:58:16 +0800 Message-ID: <20250116065825.1041558-2-coxu@redhat.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250116065825.1041558-1-coxu@redhat.com> References: <20250116065825.1041558-1-coxu@redhat.com> 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" Currently, kexec_buf is placed in order which means for the same machine, the info in the kexec_buf is always located at the same position each time the machine is booted. This may cause a risk for sensitive information like LUKS volume key. Now struct kexec_buf has a new field random which indicates it's supposed to be placed in a random position. Note this feature is enabled only when CONFIG_CRASH_DUMP is enabled. So it only takes effect for kdump and won't impact kexec reboot. Suggested-by: Jan Pazdziora Signed-off-by: Coiby Xu --- include/linux/kexec.h | 30 ++++++++++++++++++++++++++++++ kernel/kexec_file.c | 3 +++ 2 files changed, 33 insertions(+) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index f0e9f8eda7a3..61269e97502a 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -25,6 +25,10 @@ =20 extern note_buf_t __percpu *crash_notes; =20 +#ifdef CONFIG_CRASH_DUMP +#include +#endif + #ifdef CONFIG_KEXEC_CORE #include #include @@ -171,6 +175,7 @@ int kexec_image_post_load_cleanup_default(struct kimage= *image); * @buf_min: The buffer can't be placed below this address. * @buf_max: The buffer can't be placed above this address. * @top_down: Allocate from top of memory. + * @random: Place the buffer at a random position. */ struct kexec_buf { struct kimage *image; @@ -182,8 +187,33 @@ struct kexec_buf { unsigned long buf_min; unsigned long buf_max; bool top_down; +#ifdef CONFIG_CRASH_DUMP + bool random; +#endif }; =20 + +#ifdef CONFIG_CRASH_DUMP +static inline void kexec_random_range_start(unsigned long start, + unsigned long end, + struct kexec_buf *kbuf, + unsigned long *temp_start) +{ + unsigned short i; + + if (kbuf->random) { + get_random_bytes(&i, sizeof(unsigned short)); + *temp_start =3D start + (end - start) / USHRT_MAX * i; + } +} +#else +static inline void kexec_random_range_start(unsigned long start, + unsigned long end, + struct kexec_buf *kbuf, + unsigned long *temp_start) +{} +#endif + int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf); int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name, void *buf, unsigned int size, diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index 3eedb8c226ad..875fe108cc83 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -445,6 +445,7 @@ static int locate_mem_hole_top_down(unsigned long start= , unsigned long end, =20 temp_end =3D min(end, kbuf->buf_max); temp_start =3D temp_end - kbuf->memsz + 1; + kexec_random_range_start(temp_start, temp_end, kbuf, &temp_start); =20 do { /* align down start */ @@ -483,6 +484,8 @@ static int locate_mem_hole_bottom_up(unsigned long star= t, unsigned long end, =20 temp_start =3D max(start, kbuf->buf_min); =20 + kexec_random_range_start(temp_start, end, kbuf, &temp_start); + do { temp_start =3D ALIGN(temp_start, kbuf->buf_align); temp_end =3D temp_start + kbuf->memsz - 1; --=20 2.47.1