[PATCH bpf-next 1/8] bpf: move unprivileged checks into map_create() and bpf_prog_load()

[Andrii Nakryiko]

Make each bpf() syscall command a bit more self-contained, making it
easier to further enhance it. We move sysctl_unprivileged_bpf_disabled
handling down to map_create() and bpf_prog_load(), two special commands
in this regard.

Signed-off-by: Andrii Nakryiko <andrii at kernel.org>
---
 kernel/bpf/syscall.c | 37 ++++++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6d575505f89c..c1d268025985 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1130,6 +1130,17 @@ static int map_create(union bpf_attr *attr)
 	int f_flags;
 	int err;
 
+	/* Intent here is for unprivileged_bpf_disabled to block key object
+	 * creation commands for unprivileged users; other actions depend
+	 * of fd availability and access to bpffs, so are dependent on
+	 * object creation success.  Capabilities are later verified for
+	 * operations such as load and map create, so even with unprivileged
+	 * BPF disabled, capability checks are still carried out for these
+	 * and other operations.
+	 */
+	if (!bpf_capable() && sysctl_unprivileged_bpf_disabled)
+		return -EPERM;
+
 	err = CHECK_ATTR(BPF_MAP_CREATE);
 	if (err)
 		return -EINVAL;
@@ -2512,6 +2523,17 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	char license[128];
 	bool is_gpl;
 
+	/* Intent here is for unprivileged_bpf_disabled to block key object
+	 * creation commands for unprivileged users; other actions depend
+	 * of fd availability and access to bpffs, so are dependent on
+	 * object creation success.  Capabilities are later verified for
+	 * operations such as load and map create, so even with unprivileged
+	 * BPF disabled, capability checks are still carried out for these
+	 * and other operations.
+	 */
+	if (!bpf_capable() && sysctl_unprivileged_bpf_disabled)
+		return -EPERM;
+
 	if (CHECK_ATTR(BPF_PROG_LOAD))
 		return -EINVAL;
 
@@ -5008,23 +5030,8 @@ static int bpf_prog_bind_map(union bpf_attr *attr)
 static int __sys_bpf(int cmd, bpfptr_t uattr, unsigned int size)
 {
 	union bpf_attr attr;
-	bool capable;
 	int err;
 
-	capable = bpf_capable() || !sysctl_unprivileged_bpf_disabled;
-
-	/* Intent here is for unprivileged_bpf_disabled to block key object
-	 * creation commands for unprivileged users; other actions depend
-	 * of fd availability and access to bpffs, so are dependent on
-	 * object creation success.  Capabilities are later verified for
-	 * operations such as load and map create, so even with unprivileged
-	 * BPF disabled, capability checks are still carried out for these
-	 * and other operations.
-	 */
-	if (!capable &&
-	    (cmd == BPF_MAP_CREATE || cmd == BPF_PROG_LOAD))
-		return -EPERM;
-
 	err = bpf_check_uarg_tail_zero(uattr, sizeof(attr), size);
 	if (err)
 		return err;
-- 
2.34.1