Patch "cap: fix conversions on getxattr" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    cap: fix conversions on getxattr

to the 5.10-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:
     cap-fix-conversions-on-getxattr.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8b7537a06c1e3e4f4f7ddaf713dac3c936e00865
Author: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Date:   Thu Jan 28 10:22:48 2021 +0100

    cap: fix conversions on getxattr
    
    [ Upstream commit f2b00be488730522d0fb7a8a5de663febdcefe0a ]
    
    If a capability is stored on disk in v2 format cap_inode_getsecurity() will
    currently return in v2 format unconditionally.
    
    This is wrong: v2 cap should be equivalent to a v3 cap with zero rootid,
    and so the same conversions performed on it.
    
    If the rootid cannot be mapped, v3 is returned unconverted.  Fix this so
    that both v2 and v3 return -EOVERFLOW if the rootid (or the owner of the fs
    user namespace in case of v2) cannot be mapped into the current user
    namespace.
    
    Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
    Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/security/commoncap.c b/security/commoncap.c
index 59bf3c1674c8b..a6c9bb4441d54 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -371,10 +371,11 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
 {
 	int size, ret;
 	kuid_t kroot;
+	u32 nsmagic, magic;
 	uid_t root, mappedroot;
 	char *tmpbuf = NULL;
 	struct vfs_cap_data *cap;
-	struct vfs_ns_cap_data *nscap;
+	struct vfs_ns_cap_data *nscap = NULL;
 	struct dentry *dentry;
 	struct user_namespace *fs_ns;
 
@@ -396,46 +397,61 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
 	fs_ns = inode->i_sb->s_user_ns;
 	cap = (struct vfs_cap_data *) tmpbuf;
 	if (is_v2header((size_t) ret, cap)) {
-		/* If this is sizeof(vfs_cap_data) then we're ok with the
-		 * on-disk value, so return that.  */
-		if (alloc)
-			*buffer = tmpbuf;
-		else
-			kfree(tmpbuf);
-		return ret;
-	} else if (!is_v3header((size_t) ret, cap)) {
-		kfree(tmpbuf);
-		return -EINVAL;
+		root = 0;
+	} else if (is_v3header((size_t) ret, cap)) {
+		nscap = (struct vfs_ns_cap_data *) tmpbuf;
+		root = le32_to_cpu(nscap->rootid);
+	} else {
+		size = -EINVAL;
+		goto out_free;
 	}
 
-	nscap = (struct vfs_ns_cap_data *) tmpbuf;
-	root = le32_to_cpu(nscap->rootid);
 	kroot = make_kuid(fs_ns, root);
 
 	/* If the root kuid maps to a valid uid in current ns, then return
 	 * this as a nscap. */
 	mappedroot = from_kuid(current_user_ns(), kroot);
 	if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
+		size = sizeof(struct vfs_ns_cap_data);
 		if (alloc) {
-			*buffer = tmpbuf;
+			if (!nscap) {
+				/* v2 -> v3 conversion */
+				nscap = kzalloc(size, GFP_ATOMIC);
+				if (!nscap) {
+					size = -ENOMEM;
+					goto out_free;
+				}
+				nsmagic = VFS_CAP_REVISION_3;
+				magic = le32_to_cpu(cap->magic_etc);
+				if (magic & VFS_CAP_FLAGS_EFFECTIVE)
+					nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
+				memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
+				nscap->magic_etc = cpu_to_le32(nsmagic);
+			} else {
+				/* use allocated v3 buffer */
+				tmpbuf = NULL;
+			}
 			nscap->rootid = cpu_to_le32(mappedroot);
-		} else
-			kfree(tmpbuf);
-		return size;
+			*buffer = nscap;
+		}
+		goto out_free;
 	}
 
 	if (!rootid_owns_currentns(kroot)) {
-		kfree(tmpbuf);
-		return -EOPNOTSUPP;
+		size = -EOVERFLOW;
+		goto out_free;
 	}
 
 	/* This comes from a parent namespace.  Return as a v2 capability */
 	size = sizeof(struct vfs_cap_data);
 	if (alloc) {
-		*buffer = kmalloc(size, GFP_ATOMIC);
-		if (*buffer) {
-			struct vfs_cap_data *cap = *buffer;
-			__le32 nsmagic, magic;
+		if (nscap) {
+			/* v3 -> v2 conversion */
+			cap = kzalloc(size, GFP_ATOMIC);
+			if (!cap) {
+				size = -ENOMEM;
+				goto out_free;
+			}
 			magic = VFS_CAP_REVISION_2;
 			nsmagic = le32_to_cpu(nscap->magic_etc);
 			if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
@@ -443,9 +459,12 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
 			memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 			cap->magic_etc = cpu_to_le32(magic);
 		} else {
-			size = -ENOMEM;
+			/* use unconverted v2 */
+			tmpbuf = NULL;
 		}
+		*buffer = cap;
 	}
+out_free:
 	kfree(tmpbuf);
 	return size;
 }