On Tue, Jun 28, 2022 at 04:19:48PM +0000, KP Singh wrote: > A simple test that adds an xattr on a copied /bin/ls and reads it back > when the copied ls is executed. > > Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx> > --- > .../testing/selftests/bpf/prog_tests/xattr.c | 54 +++++++++++++++++++ > tools/testing/selftests/bpf/progs/xattr.c | 37 +++++++++++++ > 2 files changed, 91 insertions(+) > create mode 100644 tools/testing/selftests/bpf/prog_tests/xattr.c > create mode 100644 tools/testing/selftests/bpf/progs/xattr.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/xattr.c b/tools/testing/selftests/bpf/prog_tests/xattr.c > new file mode 100644 > index 000000000000..ef07fa8a1763 > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/xattr.c > @@ -0,0 +1,54 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +/* > + * Copyright 2022 Google LLC. > + */ > + > +#include <test_progs.h> > +#include <sys/xattr.h> > +#include "xattr.skel.h" > + > +#define XATTR_NAME "security.bpf" > +#define XATTR_VALUE "test_progs" > + > +void test_xattr(void) > +{ > + struct xattr *skel = NULL; > + char tmp_dir_path[] = "/tmp/xattrXXXXXX"; > + char tmp_exec_path[64]; > + char cmd[256]; > + int err; > + > + if (CHECK_FAIL(!mkdtemp(tmp_dir_path))) > + goto close_prog; > + > + snprintf(tmp_exec_path, sizeof(tmp_exec_path), "%s/copy_of_ls", > + tmp_dir_path); > + snprintf(cmd, sizeof(cmd), "cp /bin/ls %s", tmp_exec_path); > + if (CHECK_FAIL(system(cmd))) > + goto close_prog_rmdir; > + > + if (CHECK_FAIL(setxattr(tmp_exec_path, XATTR_NAME, XATTR_VALUE, > + sizeof(XATTR_VALUE), 0))) > + goto close_prog_rmdir; > + > + skel = xattr__open_and_load(); > + if (!ASSERT_OK_PTR(skel, "skel_load")) > + goto close_prog_rmdir; > + > + err = xattr__attach(skel); > + if (!ASSERT_OK(err, "xattr__attach failed")) > + goto close_prog_rmdir; > + > + snprintf(cmd, sizeof(cmd), "%s -l", tmp_exec_path); > + if (CHECK_FAIL(system(cmd))) > + goto close_prog_rmdir; > + > + ASSERT_EQ(skel->bss->result, 1, "xattr result"); > + > +close_prog_rmdir: > + snprintf(cmd, sizeof(cmd), "rm -rf %s", tmp_dir_path); > + system(cmd); > +close_prog: > + xattr__destroy(skel); > +} > diff --git a/tools/testing/selftests/bpf/progs/xattr.c b/tools/testing/selftests/bpf/progs/xattr.c > new file mode 100644 > index 000000000000..ccc078fb8ebd > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/xattr.c > @@ -0,0 +1,37 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +/* > + * Copyright 2022 Google LLC. > + */ > + > +#include "vmlinux.h" > +#include <bpf/bpf_helpers.h> > +#include <bpf/bpf_tracing.h> > + > +char _license[] SEC("license") = "GPL"; > + > +#define XATTR_NAME "security.bpf" > +#define XATTR_VALUE "test_progs" > + > +__u64 result = 0; > + > +extern ssize_t bpf_getxattr(struct dentry *dentry, struct inode *inode, > + const char *name, void *value, int size) __ksym; > + > +SEC("lsm.s/bprm_committed_creds") > +void BPF_PROG(bprm_cc, struct linux_binprm *bprm) > +{ > + struct task_struct *current = bpf_get_current_task_btf(); > + char dir_xattr_value[64] = {0}; > + int xattr_sz = 0; > + > + xattr_sz = bpf_getxattr(bprm->file->f_path.dentry, > + bprm->file->f_path.dentry->d_inode, XATTR_NAME, > + dir_xattr_value, 64); Yeah, this isn't right. You're not accounting for the caller's userns nor for the idmapped mount. If this is supposed to work you will need a variant of vfs_getxattr() that takes the mount's idmapping into account afaict. See what needs to happen after do_getxattr().