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Date:   Thu, 27 Dec 2018 13:06:52 +0800
From:   Dave Young <dyoung@redhat.com>
To:     linux-kernel@vger.kernel.org, kexec@lists.infradead.org
Cc:     AKASHI Takahiro <takahiro.akashi@linaro.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Baoquan He <bhe@redhat.com>, x86@kernel.org,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vivek Goyal <vgoyal@redhat.com>
Subject: [PATCH] x86/kexec: fix a kexec_file_load failure
Message-ID: <20181227050652.GA2960@dhcp-128-65.nay.redhat.com>
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The code cleanup mentioned in Fixes tag changed the behavior of
kexec_locate_mem_hole.  The kexec_locate_mem_hole will try to
allocate free memory only when kbuf.mem is initialized as zero.

But in x86 kexec_file_load implementation there are a few places
the kbuf.mem is reused like below:
  /* kbuf initialized, kbuf.mem = 0 */
  ...
  kexec_add_buffer()
  ...
  kexec_add_buffer()

  The second kexec_add_buffer will reuse previous kbuf but not
  reinitialize the kbuf.mem.

Thus kexec_file_load failed because the sanity check failed.

So explictily reset mem = 0 to fix the issue.

Fixes: b6664ba42f14 ("s390, kexec_file: drop arch_kexec_mem_walk()")
Signed-off-by: Dave Young <dyoung@redhat.com>
Cc: <stable@vger.kernel.org>
---
 arch/x86/kernel/crash.c           | 1 +
 arch/x86/kernel/kexec-bzimage64.c | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index f631a3f15587..37147509d2c8 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -469,6 +469,7 @@ int crash_load_segments(struct kimage *image)
 
 	kbuf.memsz = kbuf.bufsz;
 	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
+	kbuf.mem = 0;
 	ret = kexec_add_buffer(&kbuf);
 	if (ret) {
 		vfree((void *)image->arch.elf_headers);
diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 278cd07228dd..558204bdf412 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -434,6 +434,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 	kbuf.memsz = PAGE_ALIGN(header->init_size);
 	kbuf.buf_align = header->kernel_alignment;
 	kbuf.buf_min = MIN_KERNEL_LOAD_ADDR;
+	kbuf.mem = 0;
 	ret = kexec_add_buffer(&kbuf);
 	if (ret)
 		goto out_free_params;
@@ -448,6 +449,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 		kbuf.bufsz = kbuf.memsz = initrd_len;
 		kbuf.buf_align = PAGE_SIZE;
 		kbuf.buf_min = MIN_INITRD_LOAD_ADDR;
+		kbuf.mem = 0;
 		ret = kexec_add_buffer(&kbuf);
 		if (ret)
 			goto out_free_params;
-- 
2.17.0