Commit beaf3d19 authored Jan 08, 2019 by Song Liu Committed by Daniel Borkmann Jan 10, 2019

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.

Fixes: 615755a7 (" bpf: extend stackmap to save binary_build_id+offset instead of address")
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent f98937c6

kernel/bpf/stackmap.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -260,7 +260,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma,
		return -EFAULT; /* page not mapped */

		ret = -EINVAL;
		page_addr = page_address(page);
		page_addr = kmap_atomic(page);
		ehdr = (Elf32_Ehdr *)page_addr;

		/* compare magic x7f "ELF" */
		@@ -276,6 +276,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma,
		else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
		ret = stack_map_get_build_id_64(page_addr, build_id);
		out:
		kunmap_atomic(page_addr);
		put_page(page);
		return ret;
		}

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