linux-kernel - [52/75] net: fix incorrect credentials passing

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Date:	Mon, 22 Apr 2013 15:25:59 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Andy Lutomirski" <luto@...capital.net>,
	"Serge E. Hallyn" <serge@...lyn.com>
Subject: [52/75] net: fix incorrect credentials passing

3.2.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@...ux-foundation.org>

commit 83f1b4ba917db5dc5a061a44b3403ddb6e783494 upstream.

Commit 257b5358b32f ("scm: Capture the full credentials of the scm
sender") changed the credentials passing code to pass in the effective
uid/gid instead of the real uid/gid.

Obviously this doesn't matter most of the time (since normally they are
the same), but it results in differences for suid binaries when the wrong
uid/gid ends up being used.

This just undoes that (presumably unintentional) part of the commit.

Reported-by: Andy Lutomirski <luto@...capital.net>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: Serge E. Hallyn <serge@...lyn.com>
Cc: David S. Miller <davem@...emloft.net>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2: scm_set_cred() does user namespace conversion
 of euid/egid using cred_to_ucred().  Add and use cred_real_to_ucred() to
 do the same thing for real uid/gid.]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/net/scm.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -50,7 +50,7 @@ static __inline__ void scm_set_cred(stru
 {
 	scm->pid  = get_pid(pid);
 	scm->cred = cred ? get_cred(cred) : NULL;
-	cred_to_ucred(pid, cred, &scm->creds);
+	cred_real_to_ucred(pid, cred, &scm->creds);
 }
 
 static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -761,6 +761,20 @@ void cred_to_ucred(struct pid *pid, cons
 }
 EXPORT_SYMBOL_GPL(cred_to_ucred);
 
+void cred_real_to_ucred(struct pid *pid, const struct cred *cred,
+			struct ucred *ucred)
+{
+	ucred->pid = pid_vnr(pid);
+	ucred->uid = ucred->gid = -1;
+	if (cred) {
+		struct user_namespace *current_ns = current_user_ns();
+
+		ucred->uid = user_ns_map_uid(current_ns, cred, cred->uid);
+		ucred->gid = user_ns_map_gid(current_ns, cred, cred->gid);
+	}
+}
+EXPORT_SYMBOL_GPL(cred_real_to_ucred);
+
 int sock_getsockopt(struct socket *sock, int level, int optname,
 		    char __user *optval, int __user *optlen)
 {
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -317,6 +317,7 @@ struct ucred {
 #define IPX_TYPE	1
 
 extern void cred_to_ucred(struct pid *pid, const struct cred *cred, struct ucred *ucred);
+extern void cred_real_to_ucred(struct pid *pid, const struct cred *cred, struct ucred *ucred);
 
 extern int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
 extern int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,

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