Introduce is_owner_or_cap() to wrap CAP_FOWNER use with fsuid check

Introduce is_owner_or_cap() macro in fs.h, and convert over relevant
users to it. This is done because we want to avoid bugs in the future
where we check for only effective fsuid of the current task against a
file's owning uid, without simultaneously checking for CAP_FOWNER as
well, thus violating its semantics.
[ XFS uses special macros and structures, and in general looked ...
untouchable, so we leave it alone -- but it has been looked over. ]

The (current->fsuid != inode->i_uid) check in generic_permission() and
exec_permission_lite() is left alone, because those operations are
covered by CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH. Similarly operations
falling under the purview of CAP_CHOWN and CAP_LEASE are also left alone.

Signed-off-by: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Cc: Al Viro <viro@ftp.linux.org.uk>
Acked-by: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

22 files changed, 32 insertions, 30 deletions

diff --git a/fs/attr.c b/fs/attr.c
index a0a0c7b..f8dfc22 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -42,7 +42,7 @@ int inode_change_ok(struct inode *inode, struct iattr *attr)
 
 	/* Make sure a caller can chmod. */
 	if (ia_valid & ATTR_MODE) {
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			goto error;
 		/* Also check the setgid bit! */
 		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
@@ -52,7 +52,7 @@ int inode_change_ok(struct inode *inode, struct iattr *attr)
 
 	/* Check for setting the inode time. */
 	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
-		if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			goto error;
 	}
 fine:
diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
index 7c420b8..e58669e 100644
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -464,7 +464,7 @@ ext2_xattr_set_acl(struct inode *inode, int type, const void *value,
 
 	if (!test_opt(inode->i_sb, POSIX_ACL))
 		return -EOPNOTSUPP;
-	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		return -EPERM;
 
 	if (value) {
diff --git a/fs/ext2/ioctl.c b/fs/ext2/ioctl.c
index e85c482..3bcd254 100644
--- a/fs/ext2/ioctl.c
+++ b/fs/ext2/ioctl.c
@@ -36,7 +36,7 @@ int ext2_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
 		if (IS_RDONLY(inode))
 			return -EROFS;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EACCES;
 
 		if (get_user(flags, (int __user *) arg))
@@ -74,7 +74,7 @@ int ext2_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
 	case EXT2_IOC_GETVERSION:
 		return put_user(inode->i_generation, (int __user *) arg);
 	case EXT2_IOC_SETVERSION:
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EPERM;
 		if (IS_RDONLY(inode))
 			return -EROFS;
diff --git a/fs/ext3/acl.c b/fs/ext3/acl.c
index 1e5038d..d34e996 100644
--- a/fs/ext3/acl.c
+++ b/fs/ext3/acl.c
@@ -489,7 +489,7 @@ ext3_xattr_set_acl(struct inode *inode, int type, const void *value,
 
 	if (!test_opt(inode->i_sb, POSIX_ACL))
 		return -EOPNOTSUPP;
-	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		return -EPERM;
 
 	if (value) {
diff --git a/fs/ext3/ioctl.c b/fs/ext3/ioctl.c
index 965006d..4a2a02c 100644
--- a/fs/ext3/ioctl.c
+++ b/fs/ext3/ioctl.c
@@ -41,7 +41,7 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
 		if (IS_RDONLY(inode))
 			return -EROFS;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EACCES;
 
 		if (get_user(flags, (int __user *) arg))
@@ -122,7 +122,7 @@ flags_err:
 		__u32 generation;
 		int err;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EPERM;
 		if (IS_RDONLY(inode))
 			return -EROFS;
@@ -181,7 +181,7 @@ flags_err:
 		if (IS_RDONLY(inode))
 			return -EROFS;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EACCES;
 
 		if (get_user(rsv_window_size, (int __user *)arg))
diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 9e88254..a8bae8c 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -489,7 +489,7 @@ ext4_xattr_set_acl(struct inode *inode, int type, const void *value,
 
 	if (!test_opt(inode->i_sb, POSIX_ACL))
 		return -EOPNOTSUPP;
-	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		return -EPERM;
 
 	if (value) {
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 500567d..7b4aa45 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -40,7 +40,7 @@ int ext4_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
 		if (IS_RDONLY(inode))
 			return -EROFS;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EACCES;
 
 		if (get_user(flags, (int __user *) arg))
@@ -121,7 +121,7 @@ flags_err:
 		__u32 generation;
 		int err;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EPERM;
 		if (IS_RDONLY(inode))
 			return -EROFS;
@@ -180,7 +180,7 @@ flags_err:
 		if (IS_RDONLY(inode))
 			return -EROFS;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EACCES;
 
 		if (get_user(rsv_window_size, (int __user *)arg))
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 8e382a5..3f22e9f 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -215,7 +215,7 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
 
 	/* O_NOATIME can only be set by the owner or superuser */
 	if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
-		if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EPERM;
 
 	/* required for strict SunOS emulation */
diff --git a/fs/generic_acl.c b/fs/generic_acl.c
index 9ccb789..995d63b 100644
--- a/fs/generic_acl.c
+++ b/fs/generic_acl.c
@@ -78,7 +78,7 @@ generic_acl_set(struct inode *inode, struct generic_acl_operations *ops,
 
 	if (S_ISLNK(inode->i_mode))
 		return -EOPNOTSUPP;
-	if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		return -EPERM;
 	if (value) {
 		acl = posix_acl_from_xattr(value, size);
diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c
index 6e80844..1047a8c 100644
--- a/fs/gfs2/acl.c
+++ b/fs/gfs2/acl.c
@@ -74,7 +74,7 @@ int gfs2_acl_validate_remove(struct gfs2_inode *ip, int access)
 {
 	if (!GFS2_SB(&ip->i_inode)->sd_args.ar_posix_acl)
 		return -EOPNOTSUPP;
-	if (current->fsuid != ip->i_inode.i_uid && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(&ip->i_inode))
 		return -EPERM;
 	if (S_ISLNK(ip->i_inode.i_mode))
 		return -EOPNOTSUPP;
diff --git a/fs/hfsplus/ioctl.c b/fs/hfsplus/ioctl.c
index 79fd104..b60c0af 100644
--- a/fs/hfsplus/ioctl.c
+++ b/fs/hfsplus/ioctl.c
@@ -38,7 +38,7 @@ int hfsplus_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
 		if (IS_RDONLY(inode))
 			return -EROFS;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EACCES;
 
 		if (get_user(flags, (int __user *)arg))
diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
index a46101e..65b3a1b 100644
--- a/fs/jffs2/acl.c
+++ b/fs/jffs2/acl.c
@@ -435,7 +435,7 @@ static int jffs2_acl_setxattr(struct inode *inode, int type, const void *value,
 	struct posix_acl *acl;
 	int rc;
 
-	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		return -EPERM;
 
 	if (value) {
diff --git a/fs/jfs/ioctl.c b/fs/jfs/ioctl.c
index fe063af..3c8663b 100644
--- a/fs/jfs/ioctl.c
+++ b/fs/jfs/ioctl.c
@@ -69,7 +69,7 @@ int jfs_ioctl(struct inode * inode, struct file * filp, unsigned int cmd,
 		if (IS_RDONLY(inode))
 			return -EROFS;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EACCES;
 
 		if (get_user(flags, (int __user *) arg))
diff --git a/fs/jfs/xattr.c b/fs/jfs/xattr.c
index b2375f0..9b7f2cd 100644
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -697,7 +697,7 @@ static int can_set_system_xattr(struct inode *inode, const char *name,
 	struct posix_acl *acl;
 	int rc;
 
-	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		return -EPERM;
 
 	/*
diff --git a/fs/namei.c b/fs/namei.c
index 5e2d98d..defaa47 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1576,7 +1576,7 @@ int may_open(struct nameidata *nd, int acc_mode, int flag)
 
 	/* O_NOATIME can only be set by the owner or superuser */
 	if (flag & O_NOATIME)
-		if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EPERM;
 
 	/*
diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c
index bd68c3f..87dcece 100644
--- a/fs/ocfs2/ioctl.c
+++ b/fs/ocfs2/ioctl.c
@@ -63,7 +63,7 @@ static int ocfs2_set_inode_attr(struct inode *inode, unsigned flags,
 		goto bail_unlock;
 
 	status = -EACCES;
-	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		goto bail_unlock;
 
 	if (!S_ISDIR(inode->i_mode))
diff --git a/fs/reiserfs/ioctl.c b/fs/reiserfs/ioctl.c
index b484d29..11a0fcc 100644
--- a/fs/reiserfs/ioctl.c
+++ b/fs/reiserfs/ioctl.c
@@ -51,8 +51,7 @@ int reiserfs_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
 			if (IS_RDONLY(inode))
 				return -EROFS;
 
-			if ((current->fsuid != inode->i_uid)
-			    && !capable(CAP_FOWNER))
+			if (!is_owner_or_cap(inode))
 				return -EPERM;
 
 			if (get_user(flags, (int __user *)arg))
@@ -81,7 +80,7 @@ int reiserfs_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
 	case REISERFS_IOC_GETVERSION:
 		return put_user(inode->i_generation, (int __user *)arg);
 	case REISERFS_IOC_SETVERSION:
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+		if (!is_owner_or_cap(inode))
 			return -EPERM;
 		if (IS_RDONLY(inode))
 			return -EROFS;
diff --git a/fs/reiserfs/xattr_acl.c b/fs/reiserfs/xattr_acl.c
index 5296a29..b7e4fa4 100644
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -21,7 +21,7 @@ xattr_set_acl(struct inode *inode, int type, const void *value, size_t size)
 
 	if (!reiserfs_posixacl(inode->i_sb))
 		return -EOPNOTSUPP;
-	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		return -EPERM;
 
 	if (value) {
diff --git a/fs/utimes.c b/fs/utimes.c
index 83a7e69..682eb63 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -106,7 +106,7 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
                 if (IS_IMMUTABLE(inode))
                         goto dput_and_out;
 
-		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER)) {
+		if (!is_owner_or_cap(inode)) {
 			if (f) {
 				if (!(f->f_mode & FMODE_WRITE))
 					goto dput_and_out;
diff --git a/fs/xattr.c b/fs/xattr.c
index 4523aca..a44fd92 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -60,8 +60,7 @@ xattr_permission(struct inode *inode, const char *name, int mask)
 		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 			return -EPERM;
 		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
-		    (mask & MAY_WRITE) && (current->fsuid != inode->i_uid) &&
-		    !capable(CAP_FOWNER))
+		    (mask & MAY_WRITE) && !is_owner_or_cap(inode))
 			return -EPERM;
 	}
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 58ce336..98205f6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -284,6 +284,7 @@ extern int dir_notify_enable;
 #include <linux/pid.h>
 #include <linux/mutex.h>
 #include <linux/sysctl.h>
+#include <linux/capability.h>
 
 #include <asm/atomic.h>
 #include <asm/semaphore.h>
@@ -990,6 +991,9 @@ enum {
 #define put_fs_excl() atomic_dec(&current->fs_excl)
 #define has_fs_excl() atomic_read(&current->fs_excl)
 
+#define is_owner_or_cap(inode)	\
+	((current->fsuid == (inode)->i_uid) || capable(CAP_FOWNER))
+
 /* not quite ready to be deprecated, but... */
 extern void lock_super(struct super_block *);
 extern void unlock_super(struct super_block *);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 78c3f98..520b999 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2318,7 +2318,7 @@ static int selinux_inode_setxattr(struct dentry *dentry, char *name, void *value
 	if (sbsec->behavior == SECURITY_FS_USE_MNTPOINT)
 		return -EOPNOTSUPP;
 
-	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
+	if (!is_owner_or_cap(inode))
 		return -EPERM;
 
 	AVC_AUDIT_DATA_INIT(&ad,FS);