From: Song Liu songliubraving@fb.com
[ Upstream commit beaf3d1901f4ea46fbd5c9d857227d99751de469 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/stackmap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 90daf285de03..d9e2483669d0 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -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; }