ima: make the kexec extra memory configurable

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 <stefanb@linux.ibm.com>
Co-developed-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Steven Chen <chenste@linux.microsoft.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com> # ppc64/kvm
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 475c3261500670fddf424b1e31f5a1915169bff4..976e75f9b9ba5274b7242c3218a1aaa295eff21d 100644 (file)
--- 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.
+
 endif

diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index ed867734ee7071bcb2f2cb4dce74c28620c6d57c..d1c9d369ba08c4268b0a419930b45aecfb407971 100644 (file)
--- 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");