bpf: fix panic in stack_map_get_build_id() on i386 and arm32

As Naresh reported, test_stacktrace_build_id() causes panic on i386 and arm32 systems. This is caused by page_address() returns NULL in certain cases. This patch fixes this error by using kmap_atomic/kunmap_atomic instead of page_address.

Song Liu committed 7 years ago

Commit beaf3d11 parent f98937c1 file · +2 −1Browse files

Unified · Split

kernel/bpf/stackmap.c+2−1

@@ -260,7 +260,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma, · 259 unmodified lines
260	260	return -EFAULT; /* page not mapped */
261	261
262	262	ret = -EINVAL;
263		− page_addr = page_address(page);
	263	+ page_addr = kmap_atomic(page);
264	264	ehdr = (Elf32_Ehdr *)page_addr;
265	265
266	266	/* compare magic x7f "ELF" */
@@ -276,6 +276,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma, · 9 unmodified lines
276	276	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
277	277	ret = stack_map_get_build_id_64(page_addr, build_id);
278	278	out:
	279	+ kunmap_atomic(page_addr);
279	280	put_page(page);
280	281	return ret;
281	282	}