coredump masking: ELF: enable core dump filtering

This patch enables core dump filtering for ELF-formatted core file.

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 295cbaa..ba24cb2 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1262,7 +1262,7 @@ static int dump_seek(struct file *file, loff_t off)
  *
  * I think we should skip something. But I am not sure how. H.J.
  */
-static int maydump(struct vm_area_struct *vma)
+static int maydump(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)
@@ -1272,15 +1272,19 @@ static int maydump(struct vm_area_struct *vma)
        if (vma->vm_flags & (VM_IO | VM_RESERVED))
                return 0;
 
-       /* Dump shared memory only if mapped from an anonymous file. */
-       if (vma->vm_flags & VM_SHARED)
-               return vma->vm_file->f_path.dentry->d_inode->i_nlink == 0;
+       /* 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 it hasn't been written to, don't write it out */
+       /* By default, if it hasn't been written to, don't write it out. */
        if (!vma->anon_vma)
-               return 0;
+               return test_bit(MMF_DUMP_MAPPED_PRIVATE, &mm_flags);
 
-       return 1;
+       return test_bit(MMF_DUMP_ANON_PRIVATE, &mm_flags);
 }
 
 /* An ELF note in memory */
@@ -1572,6 +1576,7 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
 #endif
        int thread_status_size = 0;
        elf_addr_t *auxv;
+       unsigned long mm_flags;
 #ifdef ELF_CORE_WRITE_EXTRA_NOTES
        int extra_notes_size;
 #endif
@@ -1715,6 +1720,13 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
 
        dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
 
+       /*
+        * We must use the same mm->flags while dumping core to avoid
+        * inconsistency between the program headers and bodies, otherwise an
+        * unusable core file can be generated.
+        */
+       mm_flags = current->mm->flags;
+
        /* Write program headers for segments dump */
        for (vma = first_vma(current, gate_vma); vma != NULL;
                        vma = next_vma(vma, gate_vma)) {
@@ -1727,7 +1739,7 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
                phdr.p_offset = offset;
                phdr.p_vaddr = vma->vm_start;
                phdr.p_paddr = 0;
-               phdr.p_filesz = maydump(vma) ? sz : 0;
+               phdr.p_filesz = maydump(vma, mm_flags) ? sz : 0;
                phdr.p_memsz = sz;
                offset += phdr.p_filesz;
                phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0;
@@ -1771,7 +1783,7 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
                        vma = next_vma(vma, gate_vma)) {
                unsigned long addr;
 
-               if (!maydump(vma))
+               if (!maydump(vma, mm_flags))
                        continue;
 
                for (addr = vma->vm_start;