[RFC PATCH] fs/binfmt_elf.c: fix inconsistent vma dump size

[Jungseung Lee <js07.lee@gmail.com>]

vma_dump_size() has been used several times on actual dumper
and it is supposed to be same values for same vma.
But vma_dump_size() could be different, while coredump is procceeded.
(e.g. remove shared memory)

In that case, header info and vma size could be inconsistent
and it cause wrong coredump file creation.

Fix the problem by always using the same vma dump size
which is stored in vma_filsz.

Signed-off-by: Jungseung Lee <js07.lee@gmail.com>
---
 fs/binfmt_elf.c | 40 ++++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index d8fc060..3ba08ca 100644
--- 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(sizeof(*vma_filesz) * (segs - 1), 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:
-- 
1.9.1