1 files changed, 53 insertions, 25 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 66cd711a6b1a..4263326ede04 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1201,35 +1201,68 @@ static int dump_seek(struct file *file, loff_t off)
 }
 
 /*
- * Decide whether a segment is worth dumping; default is yes to be
- * sure (missing info is worse than too much; etc).
- * Personally I'd include everything, and use the coredump limit...
- *
- * I think we should skip something. But I am not sure how. H.J.
+ * Decide what to dump of a segment, part, all or none.
  */
-static int maydump(struct vm_area_struct *vma, unsigned long mm_flags)
+static unsigned long vma_dump_size(struct vm_area_struct *vma,
+				   unsigned long mm_flags)
 {
 	/* The vma can be set up to tell us the answer directly.  */
 	if (vma->vm_flags & VM_ALWAYSDUMP)
-		return 1;
+		goto whole;
 
 	/* Do not dump I/O mapped devices or special mappings */
 	if (vma->vm_flags & (VM_IO | VM_RESERVED))
 		return 0;
 
+#define FILTER(type)	(mm_flags & (1UL << MMF_DUMP_##type))
+
 	/* By default, dump shared memory if mapped from an anonymous file. */
 	if (vma->vm_flags & VM_SHARED) {
-		if (vma->vm_file->f_path.dentry->d_inode->i_nlink == 0)
-			return test_bit(MMF_DUMP_ANON_SHARED, &mm_flags);
-		else
-			return test_bit(MMF_DUMP_MAPPED_SHARED, &mm_flags);
+		if (vma->vm_file->f_path.dentry->d_inode->i_nlink == 0 ?
+		    FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
+			goto whole;
+		return 0;
 	}
 
-	/* By default, if it hasn't been written to, don't write it out. */
-	if (!vma->anon_vma)
-		return test_bit(MMF_DUMP_MAPPED_PRIVATE, &mm_flags);
+	/* Dump segments that have been written to.  */
+	if (vma->anon_vma && FILTER(ANON_PRIVATE))
+		goto whole;
+	if (vma->vm_file == NULL)
+		return 0;
 
-	return test_bit(MMF_DUMP_ANON_PRIVATE, &mm_flags);
+	if (FILTER(MAPPED_PRIVATE))
+		goto whole;
+
+	/*
+	 * If this looks like the beginning of a DSO or executable mapping,
+	 * check for an ELF header.  If we find one, dump the first page to
+	 * aid in determining what was mapped here.
+	 */
+	if (FILTER(ELF_HEADERS) && vma->vm_file != NULL && vma->vm_pgoff == 0) {
+		u32 __user *header = (u32 __user *) vma->vm_start;
+		u32 word;
+		/*
+		 * Doing it this way gets the constant folded by GCC.
+		 */
+		union {
+			u32 cmp;
+			char elfmag[SELFMAG];
+		} magic;
+		BUILD_BUG_ON(SELFMAG != sizeof word);
+		magic.elfmag[EI_MAG0] = ELFMAG0;
+		magic.elfmag[EI_MAG1] = ELFMAG1;
+		magic.elfmag[EI_MAG2] = ELFMAG2;
+		magic.elfmag[EI_MAG3] = ELFMAG3;
+		if (get_user(word, header) == 0 && word == magic.cmp)
+			return PAGE_SIZE;
+	}
+
+#undef	FILTER
+
+	return 0;
+
+whole:
+	return vma->vm_end - vma->vm_start;
 }
 
 /* An ELF note in memory */
@@ -1669,16 +1702,13 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file, un
 	for (vma = first_vma(current, gate_vma); vma != NULL;
 			vma = next_vma(vma, gate_vma)) {
 		struct elf_phdr phdr;
-		size_t sz;
-
-		sz = vma->vm_end - vma->vm_start;
 
 		phdr.p_type = PT_LOAD;
 		phdr.p_offset = offset;
 		phdr.p_vaddr = vma->vm_start;
 		phdr.p_paddr = 0;
-		phdr.p_filesz = maydump(vma, mm_flags) ? sz : 0;
-		phdr.p_memsz = sz;
+		phdr.p_filesz = vma_dump_size(vma, mm_flags);
+		phdr.p_memsz = vma->vm_end - vma->vm_start;
 		offset += phdr.p_filesz;
 		phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0;
 		if (vma->vm_flags & VM_WRITE)
@@ -1718,13 +1748,11 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file, un
 	for (vma = first_vma(current, gate_vma); vma != NULL;
 			vma = next_vma(vma, gate_vma)) {
 		unsigned long addr;
+		unsigned long end;
 
-		if (!maydump(vma, mm_flags))
-			continue;
+		end = vma->vm_start + vma_dump_size(vma, mm_flags);
 
-		for (addr = vma->vm_start;
-		     addr < vma->vm_end;
-		     addr += PAGE_SIZE) {
+		for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) {
 			struct page *page;
 			struct vm_area_struct *vma;