[PATCH v2 bpf-next 13/18] bpf: keep BPF_PROG_LOAD permission checks clear of validations

Andrii Nakryiko
2023-06-07T23:54:33Z

Move out flags validation and license checks out of the permission
checks. They were intermingled, which makes subsequent changes harder.
Clean this up: perform straightforward flag validation upfront, and
fetch and check license later, right where we use it. Also consolidate
capabilities check in one block, right after basic attribute sanity
checks.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
kernel/bpf/syscall.c | 21 +++++++++------------
1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2d9f971ec227..8e5c42af978c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2582,7 +2582,6 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
struct btf *attach_btf = NULL;
int err;
char license[128];
- bool is_gpl;

if (CHECK_ATTR(BPF_PROG_LOAD))
return -EINVAL;
@@ -2601,16 +2600,6 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
!bpf_capable())
return -EPERM;

- /* copy eBPF program license from user space */
- if (strncpy_from_bpfptr(license,
- make_bpfptr(attr->license, uattr.is_kernel),
- sizeof(license) - 1) < 0)
- return -EFAULT;
- license[sizeof(license) - 1] = 0;
-
- /* eBPF programs must be GPL compatible to use GPL-ed functions */
- is_gpl = license_is_gpl_compatible(license);
-
/* Intent here is for unprivileged_bpf_disabled to block BPF program
* creation for unprivileged users; other actions depend
* on fd availability and access to bpffs, so are dependent on
@@ -2703,12 +2692,20 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
make_bpfptr(attr->insns, uattr.is_kernel),
bpf_prog_insn_size(prog)) != 0)
goto free_prog_sec;
+ /* copy eBPF program license from user space */
+ if (strncpy_from_bpfptr(license,
+ make_bpfptr(attr->license, uattr.is_kernel),
+ sizeof(license) - 1) < 0)
+ goto free_prog_sec;
+ license[sizeof(license) - 1] = 0;
+
+ /* eBPF programs must be GPL compatible to use GPL-ed functions */
+ prog->gpl_compatible = license_is_gpl_compatible(license) ? 1 : 0;

prog->orig_prog = NULL;
prog->jited = 0;

atomic64_set(&prog->aux->refcnt, 1);
- prog->gpl_compatible = is_gpl ? 1 : 0;

if (bpf_prog_is_dev_bound(prog->aux)) {
err = bpf_prog_dev_bound_init(prog, attr);
--
2.34.1