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Commit 52f5592e authored by Jungseung Lee's avatar Jungseung Lee Committed by Linus Torvalds
Browse files

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: default avatarJungseung Lee <js07.lee@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f7e1ad1a

fs/binfmt_elf.c

+22 −18
Original line number Diff line number Diff line
@@ -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 @@ static int elf_core_dump(struct coredump_params *cprm) 
cleanup:

	free_note_info(&info);

	kfree(shdr4extnum);

	kfree(vma_filesz);

	kfree(phdr4note);

	kfree(elf);

out: