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Thu, 15 Oct 2026 20:09:49 -0700 (PDT) From: Wandun Chen To: robh@kernel.org, baoquan.he@linux.dev, rppt@kernel.org, m.szyprowski@samsung.com Cc: catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, chenhuacai@kernel.org, kernel@xen0n.name, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, saravanak@kernel.org, akpm@linux-foundation.org, pasha.tatashin@soleen.com, pratyush@kernel.org, ruirui.yang@linux.dev, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, iommu@lists.linux.dev Subject: [PATCH v8 3/8] crash_core: serialize crash header preparation against hotplug Date: Fri, 16 Oct 2026 11:08:50 +0800 Message-ID: <20261016030855.4062882-4-chenwandun1@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261016030855.4062882-1-chenwandun1@gmail.com> References: <20261016030855.4062882-1-chenwandun1@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Wandun Chen crash_prepare_headers() counts memory ranges before populating the allocated crash_mem array. The weak implementation used by ARM64, RISC-V and LoongArch walks memblock.memory, while x86 performs the same two-pass operation over system RAM resources. Concurrent memory hotplug can change range source between the two walks and make the populate pass overflow cmem->ranges. Take device_hotplug_lock when preparing crash headers during kexec_file_load(). The x86/riscv memory hotplug path already takes device_hotplug_lock, so call __crash_prepare_headers() directly to avoid recursive locking. Sashiko reported this issue in [1]. Fixes: 3751e728cef2 ("arm64: kexec_file: add crash dump support") Fixes: 1bcca8620a91 ("LoongArch: Add crash dump support for kexec_file") Fixes: 8acea455fafa ("RISC-V: Support for kexec_file on panic") Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call") Signed-off-by: Wandun Chen Link: https://sashiko.dev/#/message/20260806101002.1F84E1F000E9@smtp.kernel.org [1] Acked-by: Baoquan He --- arch/riscv/kernel/crash.c | 2 +- arch/x86/kernel/crash.c | 2 +- include/linux/crash_core.h | 2 ++ kernel/crash_core.c | 17 +++++++++++++++-- 4 files changed, 19 insertions(+), 4 deletions(-) diff --git a/arch/riscv/kernel/crash.c b/arch/riscv/kernel/crash.c index fe5a4b306aae..ac8df2edf2a7 100644 --- a/arch/riscv/kernel/crash.c +++ b/arch/riscv/kernel/crash.c @@ -70,7 +70,7 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) * Create the new elfcorehdr reflecting the changes to CPU and/or * memory resources. */ - if (crash_prepare_headers(true, &elfbuf, &elfsz, NULL)) { + if (__crash_prepare_headers(true, &elfbuf, &elfsz, NULL)) { pr_err("unable to create new elfcorehdr"); goto out; } diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index e6f23933a6df..bef008a0cb22 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -465,7 +465,7 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) * Create the new elfcorehdr reflecting the changes to CPU and/or * memory resources. */ - if (crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz, NULL)) { + if (__crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz, NULL)) { pr_err("unable to create new elfcorehdr"); goto out; } diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h index bc087124cd78..28e7a81cf263 100644 --- a/include/linux/crash_core.h +++ b/include/linux/crash_core.h @@ -61,6 +61,8 @@ extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_ma void **addr, unsigned long *sz); extern int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, unsigned long *nr_mem_ranges); +int __crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, + unsigned long *nr_mem_ranges); extern int crash_exclude_core_ranges(struct crash_mem **cmem); struct kimage; diff --git a/kernel/crash_core.c b/kernel/crash_core.c index faa0f22dbb41..8a861a946e26 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include #include @@ -344,8 +345,8 @@ int crash_exclude_core_ranges(struct crash_mem **cmem) return 0; } -int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, - unsigned long *nr_mem_ranges) +int __crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, + unsigned long *nr_mem_ranges) { unsigned int max_nr_ranges; struct crash_mem *cmem; @@ -382,6 +383,18 @@ int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, return ret; } +int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, + unsigned long *nr_mem_ranges) +{ + int ret; + + lock_device_hotplug(); + ret = __crash_prepare_headers(need_kernel_map, addr, sz, nr_mem_ranges); + unlock_device_hotplug(); + + return ret; +} + /** * crash_exclude_mem_range - exclude a mem range for existing ranges * @mem: mem->range contains an array of ranges sorted in ascending order -- 2.43.0