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authorXunlei Pang <xlpang@redhat.com>2016-05-23 16:24:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-23 17:04:14 -0700
commit9b492cf58077a0254eb4b9574029ac6e79add9f9 (patch)
tree7f723acccb7706d1c38aa4573f469d5b633cf20c
parent9eb8a659dea694b0dcbd6287f6b1fbdc523b80bc (diff)
downloadlinux-9b492cf58077a0254eb4b9574029ac6e79add9f9.tar.gz
kexec: introduce a protection mechanism for the crashkernel reserved memory
For the cases that some kernel (module) path stamps the crash reserved memory(already mapped by the kernel) where has been loaded the second kernel data, the kdump kernel will probably fail to boot when panic happens (or even not happens) leaving the culprit at large, this is unacceptable. The patch introduces a mechanism for detecting such cases: 1) After each crash kexec loading, it simply marks the reserved memory regions readonly since we no longer access it after that. When someone stamps the region, the first kernel will panic and trigger the kdump. The weak arch_kexec_protect_crashkres() is introduced to do the actual protection. 2) To allow multiple loading, once 1) was done we also need to remark the reserved memory to readwrite each time a system call related to kdump is made. The weak arch_kexec_unprotect_crashkres() is introduced to do the actual protection. The architecture can make its specific implementation by overriding arch_kexec_protect_crashkres() and arch_kexec_unprotect_crashkres(). Signed-off-by: Xunlei Pang <xlpang@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Dave Young <dyoung@redhat.com> Cc: Minfei Huang <mhuang@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Baoquan He <bhe@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/kexec.h2
-rw-r--r--kernel/kexec.c9
-rw-r--r--kernel/kexec_core.c6
-rw-r--r--kernel/kexec_file.c8
4 files changed, 23 insertions, 2 deletions
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 2cc643c6e870..643ff4a3fbf6 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -317,6 +317,8 @@ int __weak arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr,
Elf_Shdr *sechdrs, unsigned int relsec);
int __weak arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
unsigned int relsec);
+void arch_kexec_protect_crashkres(void);
+void arch_kexec_unprotect_crashkres(void);
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
diff --git a/kernel/kexec.c b/kernel/kexec.c
index ee70aef5cd81..b44cb3f5a15c 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -167,8 +167,12 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
return -EBUSY;
dest_image = &kexec_image;
- if (flags & KEXEC_ON_CRASH)
+ if (flags & KEXEC_ON_CRASH) {
dest_image = &kexec_crash_image;
+ if (kexec_crash_image)
+ arch_kexec_unprotect_crashkres();
+ }
+
if (nr_segments > 0) {
unsigned long i;
@@ -211,6 +215,9 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
image = xchg(dest_image, image);
out:
+ if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
+ arch_kexec_protect_crashkres();
+
mutex_unlock(&kexec_mutex);
kimage_free(image);
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index d5d408252992..48b73cc8e425 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1563,3 +1563,9 @@ void __weak crash_map_reserved_pages(void)
void __weak crash_unmap_reserved_pages(void)
{}
+
+void __weak arch_kexec_protect_crashkres(void)
+{}
+
+void __weak arch_kexec_unprotect_crashkres(void)
+{}
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index c72d2ff5896e..503bc2d348e5 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -274,8 +274,11 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
return -EBUSY;
dest_image = &kexec_image;
- if (flags & KEXEC_FILE_ON_CRASH)
+ if (flags & KEXEC_FILE_ON_CRASH) {
dest_image = &kexec_crash_image;
+ if (kexec_crash_image)
+ arch_kexec_unprotect_crashkres();
+ }
if (flags & KEXEC_FILE_UNLOAD)
goto exchange;
@@ -324,6 +327,9 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
exchange:
image = xchg(dest_image, image);
out:
+ if ((flags & KEXEC_FILE_ON_CRASH) && kexec_crash_image)
+ arch_kexec_protect_crashkres();
+
mutex_unlock(&kexec_mutex);
kimage_free(image);
return ret;