Patch "selinux: do not check open permission on sockets" has been added to the 4.4-stable tree

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

selinux: do not check open permission on sockets

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:
selinux-do-not-check-open-permission-on-sockets.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.

From: Stephen Smalley <[email protected]>
Date: Fri, 12 May 2017 12:41:24 -0400
Subject: selinux: do not check open permission on sockets

From: Stephen Smalley <[email protected]>

[ Upstream commit ccb544781d34afdb73a9a73ae53035d824d193bf ]

open permission is currently only defined for files in the kernel (COMMON_FILE_PERMS rather than COMMON_FILE_SOCK_PERMS). Construction of an artificial test case that tries to open a socket via /proc/pid/fd will generate a recvfrom avc denial because recvfrom and open happen to map to the same permission bit in socket vs file classes.

open of a socket via /proc/pid/fd is not supported by the kernel regardless and will ultimately return ENXIO. But we hit the permission check first and can thus produce these odd/misleading denials. Omit the open check when operating on a socket.

---
 security/selinux/hooks.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

@@ -1942,8 +1942,9 @@ static inline u32 file_to_av(struct file
 static inline u32 open_file_to_av(struct file *file)
 {
 	u32 av = file_to_av(file);
+	struct inode *inode = file_inode(file);
 
-	if (selinux_policycap_openperm)
+	if (selinux_policycap_openperm && inode->i_sb->s_magic != SOCKFS_MAGIC)
 		av |= FILE__OPEN;
 
 	return av;

@@ -2912,6 +2913,7 @@ static int selinux_inode_permission(stru
 static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)
 {
 	const struct cred *cred = current_cred();
+	struct inode *inode = d_backing_inode(dentry);
 	unsigned int ia_valid = iattr->ia_valid;
 	__u32 av = FILE__WRITE;
 

@@ -2927,8 +2929,10 @@ static int selinux_inode_setattr(struct
 			ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_TIMES_SET))
 		return dentry_has_perm(cred, dentry, FILE__SETATTR);
 
-	if (selinux_policycap_openperm && (ia_valid & ATTR_SIZE)
-			&& !(ia_valid & ATTR_FILE))
+	if (selinux_policycap_openperm &&
+	    inode->i_sb->s_magic != SOCKFS_MAGIC &&
+	    (ia_valid & ATTR_SIZE) &&
+	    !(ia_valid & ATTR_FILE))
 		av |= FILE__OPEN;
 
 	return dentry_has_perm(cred, dentry, av);

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

queue-4.4/selinux-do-not-check-open-permission-on-sockets.patch