fs/binfmt_elf.c: fix internal inconsistency relating to vma dump size

vma_dump_size() has been used several times on actual dumper and it is
supposed to return the same value for the same vma.  But vma_dump_size()
could return different values for same vma.

The known problem case is concurrent shared memory removal.  If a vma is
used for a shared memory and that shared memory is removed between
writing program header and dumping vma memory, this will result in a
dump file which is internally consistent.

To fix the problem, we set baseline to get dump size and store the size
into vma_filesz and always use the same vma dump size which is stored in
vma_filsz.  The consistnecy with reality is not actually guranteed, but
it's tolerable since that is fully consistent with base line.

Signed-off-by: Jungseung Lee <js07.lee@gmail.com>
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 d8fc0605b9d23039b558cc4d1327a40c246caa09..3a6175fe10c015cf862912a32ba8d45d75cc3b2f 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1994,18 +1994,6 @@ static void fill_extnum_info(struct elfhdr *elf, struct elf_shdr *shdr4extnum,
        shdr4extnum->sh_info = segs;
 }
 
-static size_t elf_core_vma_data_size(struct vm_area_struct *gate_vma,
-                                    unsigned long mm_flags)
-{
-       struct vm_area_struct *vma;
-       size_t size = 0;
-
-       for (vma = first_vma(current, gate_vma); vma != NULL;
-            vma = next_vma(vma, gate_vma))
-               size += vma_dump_size(vma, mm_flags);
-       return size;
-}
-
 /*
  * Actual dumper
  *
@@ -2017,7 +2005,8 @@ static int elf_core_dump(struct coredump_params *cprm)
 {
        int has_dumped = 0;
        mm_segment_t fs;
-       int segs;
+       int segs, i;
+       size_t vma_data_size = 0;
        struct vm_area_struct *vma, *gate_vma;
        struct elfhdr *elf = NULL;
        loff_t offset = 0, dataoff;
@@ -2026,6 +2015,7 @@ static int elf_core_dump(struct coredump_params *cprm)
        struct elf_shdr *shdr4extnum = NULL;
        Elf_Half e_phnum;
        elf_addr_t e_shoff;
+       elf_addr_t *vma_filesz = NULL;
 
        /*
         * We no longer stop all VM operations.
@@ -2093,7 +2083,20 @@ static int elf_core_dump(struct coredump_params *cprm)
 
        dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
 
-       offset += elf_core_vma_data_size(gate_vma, cprm->mm_flags);
+       vma_filesz = kmalloc_array(segs - 1, sizeof(*vma_filesz), GFP_KERNEL);
+       if (!vma_filesz)
+               goto end_coredump;
+
+       for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
+                       vma = next_vma(vma, gate_vma)) {
+               unsigned long dump_size;
+
+               dump_size = vma_dump_size(vma, cprm->mm_flags);
+               vma_filesz[i++] = dump_size;
+               vma_data_size += dump_size;
+       }
+
+       offset += vma_data_size;
        offset += elf_core_extra_data_size();
        e_shoff = offset;
 
@@ -2113,7 +2116,7 @@ static int elf_core_dump(struct coredump_params *cprm)
                goto end_coredump;
 
        /* Write program headers for segments dump */
-       for (vma = first_vma(current, gate_vma); vma != NULL;
+       for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
                        vma = next_vma(vma, gate_vma)) {
                struct elf_phdr phdr;
 
@@ -2121,7 +2124,7 @@ static int elf_core_dump(struct coredump_params *cprm)
                phdr.p_offset = offset;
                phdr.p_vaddr = vma->vm_start;
                phdr.p_paddr = 0;
-               phdr.p_filesz = vma_dump_size(vma, cprm->mm_flags);
+               phdr.p_filesz = vma_filesz[i++];
                phdr.p_memsz = vma->vm_end - vma->vm_start;
                offset += phdr.p_filesz;
                phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0;
@@ -2149,12 +2152,12 @@ static int elf_core_dump(struct coredump_params *cprm)
        if (!dump_skip(cprm, dataoff - cprm->written))
                goto end_coredump;
 
-       for (vma = first_vma(current, gate_vma); vma != NULL;
+       for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
                        vma = next_vma(vma, gate_vma)) {
                unsigned long addr;
                unsigned long end;
 
-               end = vma->vm_start + vma_dump_size(vma, cprm->mm_flags);
+               end = vma->vm_start + vma_filesz[i++];
 
                for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) {
                        struct page *page;
@@ -2187,6 +2190,7 @@ end_coredump:
 cleanup:
        free_note_info(&info);
        kfree(shdr4extnum);
+       kfree(vma_filesz);
        kfree(phdr4note);
        kfree(elf);
 out: