[PATCH 13/16] kexec: Allow only signed processes to call sys_kexec() in secureboot mode

[Vivek Goyal]

Modify sys_kexec() so that it allows only signed processes to execute
sys_kexec() when secureboot is enabled.

Signed-off-by: Vivek Goyal <vgo...@redhat.com>
---
 kernel/kexec.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 59f7b55..478566e 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -907,6 +907,31 @@ static int kimage_load_segment(struct kimage *image,
        return result;
 }
 
+static int check_task_signature(void)
+{
+       int ret = 0;
+       const struct cred *cred;
+
+       /* If secureboot is enabled, There are extra checks required */
+       /* TODO: Change it once secure_level patches stablize */
+/*
+       if (!secure_modules())
+               return ret;
+*/
+       /*
+        * Calling process should be signed, memlocked.
+        */
+
+       if (!test_bit(MMF_VM_LOCKED, &current->mm->flags))
+               return -EPERM;
+
+       cred = current_cred();
+       if (!cred->proc_signed)
+               return -EPERM;
+
+       return ret;
+}
+
 /*
  * Exec Kernel system call: for obvious reasons only root may call it.
  *
@@ -942,6 +967,10 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned 
long, nr_segments,
        if (!capable(CAP_SYS_BOOT))
                return -EPERM;
 
+       result = check_task_signature();
+       if (result)
+               return result;
+
        /*
         * Verify we have a legal set of flags
         * This leaves us room for future extensions.
-- 
1.8.3.1

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