Commit beaf3d19 authored by Song Liu's avatar Song Liu Committed by Daniel Borkmann
Browse files

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: default avatarNaresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarDaniel 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;

}