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Commit 86a2bb5a authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

coredump: fix spam with zero VMA process 

Nobody ever tried to self destruct by unmapping whole address space at
once:

	munmap((void *)0, (1ULL << 47) - 4096);

Doing this produces 2 warnings for zero-length vmalloc allocations:

  a.out[1353]: segfault at 7f80bcc4b757 ip 00007f80bcc4b757 sp 00007fff683939b8 error 14
  a.out: vmalloc: allocation failure: 0 bytes, mode:0xcc0(GFP_KERNEL), nodemask=(null)
	...
  a.out: vmalloc: allocation failure: 0 bytes, mode:0xcc0(GFP_KERNEL), nodemask=(null)
	...

Fix is to switch to kvmalloc().

Steps to reproduce:

	// vsyscall=none
	#include <sys/mman.h>
	#include <sys/resource.h>
	int main(void)
	{
		setrlimit(RLIMIT_CORE, &(struct rlimit){RLIM_INFINITY, RLIM_INFINITY});
		munmap((void *)0, (1ULL << 47) - 4096);
		return 0;
	}

Link: http://lkml.kernel.org/r/20180410180353.GA2515@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c2574aaa

fs/binfmt_elf.c

+9 −8
Original line number Diff line number Diff line
@@ -1621,8 +1621,8 @@ static int fill_files_note(struct memelfnote *note) 
	if (size >= MAX_FILE_NOTE_SIZE) /* paranoia check */

		return -EINVAL;

	size = round_up(size, PAGE_SIZE);

	data = vmalloc(size);

	if (!data)

	data = kvmalloc(size, GFP_KERNEL);

	if (ZERO_OR_NULL_PTR(data))

		return -ENOMEM;



	start_end_ofs = data + 2;
@@ -1639,7 +1639,7 @@ static int fill_files_note(struct memelfnote *note) 
		filename = file_path(file, name_curpos, remaining);

		if (IS_ERR(filename)) {

			if (PTR_ERR(filename) == -ENAMETOOLONG) {

				vfree(data);

				kvfree(data);

				size = size * 5 / 4;

				goto alloc;

			}
@@ -1932,7 +1932,7 @@ static void free_note_info(struct elf_note_info *info) 
		kfree(t);

	}

	kfree(info->psinfo.data);

	vfree(info->files.data);

	kvfree(info->files.data);

}



#else
@@ -2148,7 +2148,7 @@ static void free_note_info(struct elf_note_info *info) 


	/* Free data possibly allocated by fill_files_note(): */

	if (info->notes_files)

		vfree(info->notes_files->data);

		kvfree(info->notes_files->data);



	kfree(info->prstatus);

	kfree(info->psinfo);
@@ -2294,8 +2294,9 @@ static int elf_core_dump(struct coredump_params *cprm) 


	if (segs - 1 > ULONG_MAX / sizeof(*vma_filesz))

		goto end_coredump;

	vma_filesz = vmalloc(array_size(sizeof(*vma_filesz), (segs - 1)));

	if (!vma_filesz)

	vma_filesz = kvmalloc(array_size(sizeof(*vma_filesz), (segs - 1)),

			      GFP_KERNEL);

	if (ZERO_OR_NULL_PTR(vma_filesz))

		goto end_coredump;



	for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
@@ -2402,7 +2403,7 @@ static int elf_core_dump(struct coredump_params *cprm) 
cleanup:

	free_note_info(&info);

	kfree(shdr4extnum);

	vfree(vma_filesz);

	kvfree(vma_filesz);

	kfree(phdr4note);

	kfree(elf);

out: