author: Jann Horn <jannh@google.com> 2020-10-15 20:12:50 -0700
committer: Linus Torvalds <torvalds@linux-foundation.org> 2020-10-16 11:11:21 -0700
commit: 429a22e776a2b9f85a2b9c53d8e647598b553dd1
parent: afc63a97b764bc5a715762d0d9cc9785c2ef4e75
Commit Summary:
Diffstat:
1 file changed, 84 insertions, 0 deletions
diff --git a/fs/coredump.c b/fs/coredump.c
index 6042d15acd51..4ef4c49a65b7 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -936,3 +936,104 @@ void dump_truncate(struct coredump_params *cprm)
}
}
EXPORT_SYMBOL(dump_truncate);
+
+/*
+ * The purpose of always_dump_vma() is to make sure that special kernel mappings
+ * that are useful for post-mortem analysis are included in every core dump.
+ * In that way we ensure that the core dump is fully interpretable later
+ * without matching up the same kernel and hardware config to see what PC values
+ * meant. These special mappings include - vDSO, vsyscall, and other
+ * architecture specific mappings
+ */
+static bool always_dump_vma(struct vm_area_struct *vma)
+{
+ /* Any vsyscall mappings? */
+ if (vma == get_gate_vma(vma->vm_mm))
+ return true;
+
+ /*
+ * Assume that all vmas with a .name op should always be dumped.
+ * If this changes, a new vm_ops field can easily be added.
+ */
+ if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
+ return true;
+
+ /*
+ * arch_vma_name() returns non-NULL for special architecture mappings,
+ * such as vDSO sections.
+ */
+ if (arch_vma_name(vma))
+ return true;
+
+ return false;
+}
+
+/*
+ * Decide how much of @vma's contents should be included in a core dump.
+ */
+unsigned long vma_dump_size(struct vm_area_struct *vma, unsigned long mm_flags)
+{
+#define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
+
+ /* always dump the vdso and vsyscall sections */
+ if (always_dump_vma(vma))
+ goto whole;
+
+ if (vma->vm_flags & VM_DONTDUMP)
+ return 0;
+
+ /* support for DAX */
+ if (vma_is_dax(vma)) {
+ if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
+ goto whole;
+ if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
+ goto whole;
+ return 0;
+ }
+
+ /* Hugetlb memory check */
+ if (is_vm_hugetlb_page(vma)) {
+ if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
+ goto whole;
+ if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
+ goto whole;
+ return 0;
+ }
+
+ /* Do not dump I/O mapped devices or special mappings */
+ if (vma->vm_flags & VM_IO)
+ return 0;
+
+ /* By default, dump shared memory if mapped from an anonymous file. */
+ if (vma->vm_flags & VM_SHARED) {
+ if (file_inode(vma->vm_file)->i_nlink == 0 ?
+ FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
+ goto whole;
+ return 0;
+ }
+
+ /* Dump segments that have been written to. */
+ if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
+ goto whole;
+ if (vma->vm_file == NULL)
+ return 0;
+
+ if (FILTER(MAPPED_PRIVATE))
+ goto whole;
+
+ /*
+ * If this is the beginning of an executable file mapping,
+ * dump the first page to aid in determining what was mapped here.
+ */
+ if (FILTER(ELF_HEADERS) &&
+ vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) &&
+ (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
+ return PAGE_SIZE;
+
+#undef FILTER
+
+ return 0;
+
+whole:
+ return vma->vm_end - vma->vm_start;
+}