1 files changed, 33 insertions, 20 deletions

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 4d76f16524cc..ac53102e244a 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1276,16 +1276,23 @@ static bool __cgroup_bpf_prog_array_is_empty(struct cgroup *cgrp,
 
 static int sockopt_alloc_buf(struct bpf_sockopt_kern *ctx, int max_optlen)
 {
-	if (unlikely(max_optlen > PAGE_SIZE) || max_optlen < 0)
+	if (unlikely(max_optlen < 0))
 		return -EINVAL;
 
+	if (unlikely(max_optlen > PAGE_SIZE)) {
+		/* We don't expose optvals that are greater than PAGE_SIZE
+		 * to the BPF program.
+		 */
+		max_optlen = PAGE_SIZE;
+	}
+
 	ctx->optval = kzalloc(max_optlen, GFP_USER);
 	if (!ctx->optval)
 		return -ENOMEM;
 
 	ctx->optval_end = ctx->optval + max_optlen;
 
-	return 0;
+	return max_optlen;
 }
 
 static void sockopt_free_buf(struct bpf_sockopt_kern *ctx)
@@ -1319,13 +1326,13 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
 	 */
 	max_optlen = max_t(int, 16, *optlen);
 
-	ret = sockopt_alloc_buf(&ctx, max_optlen);
-	if (ret)
-		return ret;
+	max_optlen = sockopt_alloc_buf(&ctx, max_optlen);
+	if (max_optlen < 0)
+		return max_optlen;
 
 	ctx.optlen = *optlen;
 
-	if (copy_from_user(ctx.optval, optval, *optlen) != 0) {
+	if (copy_from_user(ctx.optval, optval, min(*optlen, max_optlen)) != 0) {
 		ret = -EFAULT;
 		goto out;
 	}
@@ -1353,8 +1360,14 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
 		/* export any potential modifications */
 		*level = ctx.level;
 		*optname = ctx.optname;
-		*optlen = ctx.optlen;
-		*kernel_optval = ctx.optval;
+
+		/* optlen == 0 from BPF indicates that we should
+		 * use original userspace data.
+		 */
+		if (ctx.optlen != 0) {
+			*optlen = ctx.optlen;
+			*kernel_optval = ctx.optval;
+		}
 	}
 
 out:
@@ -1385,12 +1398,12 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
 	    __cgroup_bpf_prog_array_is_empty(cgrp, BPF_CGROUP_GETSOCKOPT))
 		return retval;
 
-	ret = sockopt_alloc_buf(&ctx, max_optlen);
-	if (ret)
-		return ret;
-
 	ctx.optlen = max_optlen;
 
+	max_optlen = sockopt_alloc_buf(&ctx, max_optlen);
+	if (max_optlen < 0)
+		return max_optlen;
+
 	if (!retval) {
 		/* If kernel getsockopt finished successfully,
 		 * copy whatever was returned to the user back
@@ -1404,10 +1417,8 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
 			goto out;
 		}
 
-		if (ctx.optlen > max_optlen)
-			ctx.optlen = max_optlen;
-
-		if (copy_from_user(ctx.optval, optval, ctx.optlen) != 0) {
+		if (copy_from_user(ctx.optval, optval,
+				   min(ctx.optlen, max_optlen)) != 0) {
 			ret = -EFAULT;
 			goto out;
 		}
@@ -1436,10 +1447,12 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
 		goto out;
 	}
 
-	if (copy_to_user(optval, ctx.optval, ctx.optlen) ||
-	    put_user(ctx.optlen, optlen)) {
-		ret = -EFAULT;
-		goto out;
+	if (ctx.optlen != 0) {
+		if (copy_to_user(optval, ctx.optval, ctx.optlen) ||
+		    put_user(ctx.optlen, optlen)) {
+			ret = -EFAULT;
+			goto out;
+		}
 	}
 
 	ret = ctx.retval;