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Hallyn" , Mimi Zohar , James Bottomley , Rob Herring , Saravana Kannan , Coiby Xu , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, keyrings@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org Subject: Re: [PATCH 2/4] kexec: add CRASH_ZEROIZE to wipe secrets before kdump Message-ID: References: <20260731154608.153258-1-linux@jaseg.de> <20260731154608.153258-3-linux@jaseg.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260731154608.153258-3-linux@jaseg.de> X-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: qeebyq9b1nkjdhb1nfu7mwisuyzydhxq X-Rspamd-Queue-Id: 6469BC0009 X-HE-Tag: 1786375798-247897 X-HE-Meta: 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 Rzxcukve mxEBqSa/qqOsSIxGXLBfZQQPK6vZ257uTbTeBCxsxwUYRUjFDog8IdLKkLf4Y9qoij0TOn3O2NBCGx5bUOo8THTLSAMfl9wqB3SYuARZl5fUBOA7yHPkdWJMdDyldiJgD7LJs2et6SmEPuJg4+qKHWG1vyQFtc8V9EYMXZO120Jo0RnGfZl4WZaMueFPqpGjutVYl4+QHcfqADO9+E77oZ2OQ5XIU4iO5MvdMPgmmx7Z4muTWx/rBOXLcM5s9eW83iga2g+7efUYz2A6vW/b3eQGOtazxMVUV0k/yPDN1Q0xiEly9p0heBiAlTrFn4+/FvRBz30Q7ylD4rP5yOlgP4ZEGgpFoGxVWUr2aG8h1bfIKTV1t1jSIRxwX3su0FyDJbBceZ/l8T7JPdjc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jul 31, 2026 at 05:46:06PM +0200, Jan Sebastian Götte wrote: > When kdump is used to capture system memory after a panic(), any secret > keys currently in RAM end up in the dump. Add an opt-in atomic notifier > chain, crash_zeroize_notifier_list, invoked late into __crash_kexec(). > Subsystems holding secrets can register a callback to scrub them. > > Callbacks are run after machine_crash_shutdown() has already stopped the > other CPUs and disabled preemption. Callbacks must not wait on locks, > which will never be released. > > This is a best-effort, defence-in-depth measure, not a guarantee. > Secrets in flight on the stack, in registers, in DMA buffers, or in > other places in memory are out of scope. > > Signed-off-by: Jan Sebastian Götte > --- > include/linux/crash_core.h | 5 +++++ > kernel/Kconfig.kexec | 8 ++++++++ > kernel/crash_core.c | 18 ++++++++++++++++++ > 3 files changed, 31 insertions(+) Not a request but for me 'crash_wipe' would be more intuitive than 'crash_zeroize'. What do you think? > > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h > index bc087124cd78..5c7207c0bba1 100644 > --- a/include/linux/crash_core.h > +++ b/include/linux/crash_core.h > @@ -5,6 +5,7 @@ > #include > #include > #include > +#include > > struct kimage; > > @@ -34,6 +35,10 @@ static inline void arch_kexec_protect_crashkres(void) { } > static inline void arch_kexec_unprotect_crashkres(void) { } > #endif > > +#ifdef CONFIG_CRASH_ZEROIZE > +extern struct atomic_notifier_head crash_zeroize_notifier_list; > +#endif > + > #ifndef arch_crash_handle_hotplug_event > static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { } > #endif > diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec > index 15632358bcf7..92ab0a69c8ec 100644 > --- a/kernel/Kconfig.kexec > +++ b/kernel/Kconfig.kexec > @@ -179,4 +179,12 @@ config CRASH_MAX_MEMORY_RANGES > the computation behind the value provided through the > /sys/kernel/crash_elfcorehdr_size attribute. > > +config CRASH_ZEROIZE > + bool "Zeroize secrets on panic" > + depends on CRASH_DUMP > + help > + Wipe secrets (e.g. kernel keyring and memfd_secret pages) on crash or panic. > + > + If unsure, say N. > + > endmenu > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > index 2b36aa9fade0..d3a7763e2759 100644 > --- a/kernel/crash_core.c > +++ b/kernel/crash_core.c > @@ -23,6 +23,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -33,6 +34,22 @@ > /* Per cpu memory for storing cpu states in case of system crash. */ > note_buf_t __percpu *crash_notes; > > +#ifdef CONFIG_CRASH_ZEROIZE > +ATOMIC_NOTIFIER_HEAD(crash_zeroize_notifier_list); > +EXPORT_SYMBOL_GPL(crash_zeroize_notifier_list); > + > +static void crash_zeroize(void) > +{ > + ktime_t zeroize_start = ktime_get(); > + > + pr_info("Wiping sensitive secrets...\n"); > + atomic_notifier_call_chain(&crash_zeroize_notifier_list, 0, NULL); > + pr_info("Done in %lld us\n", ktime_us_delta(ktime_get(), zeroize_start)); > +} > +#else > +static inline void crash_zeroize(void) { } > +#endif /* CONFIG_CRASH_ZEROIZE */ > + > /* time to wait for possible DMA to finish before starting the kdump kernel > * when a CMA reservation is used > */ > @@ -142,6 +159,7 @@ void __noclone __crash_kexec(struct pt_regs *regs) > crash_save_vmcoreinfo(); > machine_crash_shutdown(&fixed_regs); > crash_cma_clear_pending_dma(); > + crash_zeroize(); > machine_kexec(kexec_crash_image); > } > kexec_unlock(); > -- > 2.53.0 > BR, Jarkko