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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250429_150025_302148_A2D9A51B X-CRM114-Status: GOOD ( 24.46 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 4/29/2025 12:06 PM, Stefan Berger wrote: > > > On 4/21/25 6:25 PM, steven chen wrote: >> From: Steven Chen >> >> The extra memory allocated for carrying the IMA measurement list across >> kexec is hard-coded as half a PAGE.  Make it configurable. >> >> Define a Kconfig option, IMA_KEXEC_EXTRA_MEMORY_KB, to configure the >> extra memory (in kb) to be allocated for IMA measurements added during >> kexec soft reboot.  Ensure the default value of the option is set such >> that extra half a page of memory for additional measurements is >> allocated >> for the additional measurements. >> >> Update ima_add_kexec_buffer() function to allocate memory based on the >> Kconfig option value, rather than the currently hard-coded one. >> >> Suggested-by: Stefan Berger >> Co-developed-by: Tushar Sugandhi >> Signed-off-by: Tushar Sugandhi >> Signed-off-by: Steven Chen >> Reviewed-by: Stefan Berger >> Reviewed-by: Mimi Zohar >> Acked-by: Baoquan He >> --- >>   security/integrity/ima/Kconfig     | 11 +++++++++++ >>   security/integrity/ima/ima_kexec.c | 16 +++++++++++----- >>   2 files changed, 22 insertions(+), 5 deletions(-) >> >> diff --git a/security/integrity/ima/Kconfig >> b/security/integrity/ima/Kconfig >> index 475c32615006..976e75f9b9ba 100644 >> --- a/security/integrity/ima/Kconfig >> +++ b/security/integrity/ima/Kconfig >> @@ -321,4 +321,15 @@ config IMA_DISABLE_HTABLE >>       help >>          This option disables htable to allow measurement of >> duplicate records. >>   +config IMA_KEXEC_EXTRA_MEMORY_KB >> +    int "Extra memory for IMA measurements added during kexec soft >> reboot" >> +    range 0 40 >> +    depends on IMA_KEXEC >> +    default 0 >> +    help >> +      IMA_KEXEC_EXTRA_MEMORY_KB determines the extra memory to be >> +      allocated (in kb) for IMA measurements added during kexec soft >> reboot. >> +      If set to the default value of 0, an extra half page of memory >> for those >> +      additional measurements will be allocated. > > If you have an IMA policy taking quite a few measurements and you are > fast after reboot to log in to initiate the 'kexec load' (While system > is still starting up), the system may end up with loss of measurements > very easily if the default is 0 and pages are small. -> Set the > default to the max? Also, would we expect distros to all go through > the new config option and choose 40 or will they likely leave it at 0? > Hi Stefan, Could you please check the comments of version V11 on this default value? https://lore.kernel.org/all/20250402124725.5601-1-chenste@linux.microsoft.com/ Thanks, Steven >> + >>   endif >> diff --git a/security/integrity/ima/ima_kexec.c >> b/security/integrity/ima/ima_kexec.c >> index ed867734ee70..d1c9d369ba08 100644 >> --- a/security/integrity/ima/ima_kexec.c >> +++ b/security/integrity/ima/ima_kexec.c >> @@ -118,6 +118,7 @@ void ima_add_kexec_buffer(struct kimage *image) >>                     .buf_min = 0, .buf_max = ULONG_MAX, >>                     .top_down = true }; >>       unsigned long binary_runtime_size; >> +    unsigned long extra_memory; >>         /* use more understandable variable names than defined in >> kbuf */ >>       size_t kexec_buffer_size = 0; >> @@ -125,15 +126,20 @@ void ima_add_kexec_buffer(struct kimage *image) >>       int ret; >>         /* >> -     * Reserve an extra half page of memory for additional measurements >> -     * added during the kexec load. >> +     * Reserve extra memory for measurements added during kexec. >>        */ >> -    binary_runtime_size = ima_get_binary_runtime_size(); >> +    if (CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB <= 0) >> +        extra_memory = PAGE_SIZE / 2; >> +    else >> +        extra_memory = CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB * 1024; >> + >> +    binary_runtime_size = ima_get_binary_runtime_size() + extra_memory; >> + >>       if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE) >>           kexec_segment_size = ULONG_MAX; >>       else >> -        kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + >> -                       PAGE_SIZE / 2, PAGE_SIZE); >> +        kexec_segment_size = ALIGN(binary_runtime_size, PAGE_SIZE); >> + >>       if ((kexec_segment_size == ULONG_MAX) || >>           ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) { >>           pr_err("Binary measurement list too large.\n");