Patch "unix: correctly track in-flight fds in sending process user_struct" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Feb 29, 2016

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2016-02-29 22:45 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

unix: correctly track in-flight fds in sending process user_struct

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
unix-correctly-track-in-flight-fds-in-sending-process-user_struct.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From foo@baz Mon Feb 29 14:33:50 PST 2016

From: Hannes Frederic Sowa <[email protected]>
Date: Wed, 3 Feb 2016 02:11:03 +0100
Subject: unix: correctly track in-flight fds in sending process user_struct

From: Hannes Frederic Sowa <[email protected]>

[ Upstream commit 415e3d3e90ce9e18727e8843ae343eda5a58fad6 ]

The commit referenced in the Fixes tag incorrectly accounted the number of in-flight fds over a unix domain socket to the original opener of the file-descriptor. This allows another process to arbitrary deplete the original file-openers resource limit for the maximum of open files. Instead the sending processes and its struct cred should be credited.

To do so, we add a reference counted struct user_struct pointer to the scm_fp_list and use it to account for the number of inflight unix fds.

Fixes 712f4aad406bb1 ("unix: properly account for FDs passed over unix sockets")

Reported-by David Herrmann <[email protected]>

Cc David Herrmann <[email protected]>

Cc Willy Tarreau <[email protected]>

Cc Linus Torvalds <[email protected]>

Signed-off-by Hannes Frederic Sowa <[email protected]>

Signed-off-by David S. Miller <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 include/net/af_unix.h |    4 ++--
 include/net/scm.h     |    1 +
 net/core/scm.c        |    7 +++++++
 net/unix/af_unix.c    |    4 ++--
 net/unix/garbage.c    |    8 ++++----
 5 files changed, 16 insertions(+), 8 deletions(-)

include/net/af_unix.h +2 -2

@@ -6,8 +6,8 @@
 #include <linux/mutex.h>
 #include <net/sock.h>
 
-void unix_inflight(struct file *fp);
-void unix_notinflight(struct file *fp);
+void unix_inflight(struct user_struct *user, struct file *fp);
+void unix_notinflight(struct user_struct *user, struct file *fp);
 void unix_gc(void);
 void wait_for_unix_gc(void);
 struct sock *unix_get_socket(struct file *filp);

include/net/scm.h +1 -0

@@ -21,6 +21,7 @@ struct scm_creds {
 struct scm_fp_list {
 	short			count;
 	short			max;
+	struct user_struct	*user;
 	struct file		*fp[SCM_MAX_FD];
 };

net/core/scm.c +7 -0

@@ -87,6 +87,7 @@ static int scm_fp_copy(struct cmsghdr *c
 		*fplp = fpl;
 		fpl->count = 0;
 		fpl->max = SCM_MAX_FD;
+		fpl->user = NULL;
 	}
 	fpp = &fpl->fp[fpl->count];

@@ -107,6 +108,10 @@ static int scm_fp_copy(struct cmsghdr *c
 		*fpp++ = file;
 		fpl->count++;
 	}
+
+	if (!fpl->user)
+		fpl->user = get_uid(current_user());
+
 	return num;
 }

@@ -119,6 +124,7 @@ void __scm_destroy(struct scm_cookie *sc
 		scm->fp = NULL;
 		for (i=fpl->count-1; i>=0; i--)
 			fput(fpl->fp[i]);
+		free_uid(fpl->user);
 		kfree(fpl);
 	}
 }

@@ -336,6 +342,7 @@ struct scm_fp_list *scm_fp_dup(struct sc
 		for (i = 0; i < fpl->count; i++)
 			get_file(fpl->fp[i]);
 		new_fpl->max = new_fpl->count;
+		new_fpl->user = get_uid(fpl->user);
 	}
 	return new_fpl;
 }

net/unix/af_unix.c +2 -2

@@ -1496,7 +1496,7 @@ static void unix_detach_fds(struct scm_c
 	UNIXCB(skb).fp = NULL;
 
 	for (i = scm->fp->count-1; i >= 0; i--)
-		unix_notinflight(scm->fp->fp[i]);
+		unix_notinflight(scm->fp->user, scm->fp->fp[i]);
 }
 
 static void unix_destruct_scm(struct sk_buff *skb)

@@ -1561,7 +1561,7 @@ static int unix_attach_fds(struct scm_co
 		return -ENOMEM;
 
 	for (i = scm->fp->count - 1; i >= 0; i--)
-		unix_inflight(scm->fp->fp[i]);
+		unix_inflight(scm->fp->user, scm->fp->fp[i]);
 	return max_level;
 }

net/unix/garbage.c +4 -4

@@ -116,7 +116,7 @@ struct sock *unix_get_socket(struct file
  * descriptor if it is for an AF_UNIX socket.
  */
 
-void unix_inflight(struct file *fp)
+void unix_inflight(struct user_struct *user, struct file *fp)
 {
 	struct sock *s = unix_get_socket(fp);

@@ -133,11 +133,11 @@ void unix_inflight(struct file *fp)
 		}
 		unix_tot_inflight++;
 	}
-	fp->f_cred->user->unix_inflight++;
+	user->unix_inflight++;
 	spin_unlock(&unix_gc_lock);
 }
 
-void unix_notinflight(struct file *fp)
+void unix_notinflight(struct user_struct *user, struct file *fp)
 {
 	struct sock *s = unix_get_socket(fp);

@@ -152,7 +152,7 @@ void unix_notinflight(struct file *fp)
 			list_del_init(&u->link);
 		unix_tot_inflight--;
 	}
-	fp->f_cred->user->unix_inflight--;
+	user->unix_inflight--;
 	spin_unlock(&unix_gc_lock);
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/ipv6-udp-use-sticky-pktinfo-egress-ifindex-on-connect.patch queue-4.4/pptp-fix-illegal-memory-access-caused-by-multiple-bind-s.patch queue-4.4/ipv6-fix-a-lockdep-splat.patch queue-4.4/ipv6-addrconf-fix-recursive-spin-lock-call.patch queue-4.4/unix-correctly-track-in-flight-fds-in-sending-process-user_struct.patch queue-4.4/ipv6-enforce-flowi6_oif-usage-in-ip6_dst_lookup_tail.patch queue-4.4/route-check-and-remove-route-cache-when-we-get-route.patch