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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>
This commit is contained in:
Jungseung Lee 2014-12-10 15:52:16 -08:00 committed by Linus Torvalds
parent f7e1ad1a1e
commit 52f5592e54
1 changed files with 22 additions and 18 deletions
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40
fs/binfmt_elf.c
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@ -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: