From: Song Liu Date: Tue, 8 Jan 2019 22:20:44 +0000 (-0800) Subject: bpf: fix panic in stack_map_get_build_id() on i386 and arm32 X-Git-Tag: v4.20.13~120 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a4dc1ce0730408b45e84728982511e9ebc984d57;p=thirdparty%2Fkernel%2Fstable.git bpf: fix panic in stack_map_get_build_id() on i386 and arm32 [ 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 Signed-off-by: Song Liu Signed-off-by: Daniel Borkmann Signed-off-by: Sasha Levin --- diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 90daf285de032..d9e2483669d0b 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; }