[Devel] [PATCH 1/2] c/r: Do not crash if socket has no peercred

[Dan Smith]

Unconnected sockets don't have a valid sk_peercred yet.  If we checkpoint
them, we'll segv on the NULL pointer.

Signed-off-by: Dan Smith <danms at us.ibm.com>
---
 net/unix/checkpoint.c |   52 +++++++++++++++++++++++++++---------------------
 1 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/net/unix/checkpoint.c b/net/unix/checkpoint.c
index 708df40..25464cc 100644
--- a/net/unix/checkpoint.c
+++ b/net/unix/checkpoint.c
@@ -159,16 +159,19 @@ int unix_checkpoint(struct ckpt_ctx *ctx, struct socket *sock)
 		goto out;
 	}
 
-	/*
-	 * intentionally drop 'const' qualifier for checkpoint_obj() to
-	 * increment the usage count - it does not alter the credentials.
-	 */
-	cred = (struct cred *) get_cred(sock->sk->sk_peer_cred);
-	un->peercred = checkpoint_obj(ctx, cred, CKPT_OBJ_CRED);
-	put_cred(cred);
-	if (un->peercred < 0) {
-		ret = un->peercred;
-		goto out;
+	if (sock->sk->sk_peer_cred) {
+		/*
+		 * intentionally drop 'const' qualifier for
+		 * checkpoint_obj() to increment the usage count - it
+		 * does not alter the credentials.
+		 */
+		cred = (struct cred *) get_cred(sock->sk->sk_peer_cred);
+		un->peercred = checkpoint_obj(ctx, cred, CKPT_OBJ_CRED);
+		put_cred(cred);
+		if (un->peercred < 0) {
+			ret = un->peercred;
+			goto out;
+		}
 	}
 
 	ret = ckpt_write_obj(ctx, (struct ckpt_hdr *) un);
@@ -438,19 +441,22 @@ static int unix_restore_connected(struct ckpt_ctx *ctx,
 		addrlen = un->laddr_len;
 	}
 
-	cred = ckpt_obj_fetch(ctx, un->peercred, CKPT_OBJ_CRED);
-	if (!cred) {
-		ckpt_err(ctx, -EINVAL, "%(O)Bad peer cred\n", un->peercred);
-		return -EINVAL;
-	}
-
-	if (may_setuid(ctx->realcred->user->user_ns, cred->uid) &&
-	    may_setgid(cred->gid)) {
-		set_peercred(sk, task_tgid(current), cred);
-	} else {
-		ckpt_err(ctx, -EPERM, "peercred %i:%i would require setuid",
-			 cred->uid, cred->gid);
-		return -EPERM;
+	if (un->peercred) {
+		cred = ckpt_obj_fetch(ctx, un->peercred, CKPT_OBJ_CRED);
+		if (!cred) {
+			ckpt_err(ctx, -EINVAL,
+				 "%(O)Bad peer cred\n", un->peercred);
+			return -EINVAL;
+		}
+		if (may_setuid(ctx->realcred->user->user_ns, cred->uid) &&
+		    may_setgid(cred->gid)) {
+			set_peercred(sk, task_tgid(current), cred);
+		} else {
+			ckpt_err(ctx, -EPERM,
+				 "peercred %i:%i would require setuid",
+				 cred->uid, cred->gid);
+			return -EPERM;
+		}
 	}
 
 	if (!dead && (un->peer > 0)) {
-- 
1.7.2.2

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