From: Song Liu <songliubraving@fb.com>
Date: Tue, 8 Jan 2019 14:20:44 -0800
Subject: bpf: fix panic in stack_map_get_build_id() on i386 and arm32
Patch-mainline: v5.0-rc3
Git-commit: beaf3d1901f4ea46fbd5c9d857227d99751de469
References: bsc#1109837
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: 615755a77b24 (" 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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
kernel/bpf/stackmap.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -260,7 +260,7 @@ static int stack_map_get_build_id(struct
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
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;
}