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Date:   Fri, 25 Dec 2020 16:52:27 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>,
        Chao Yu <yuchao0@...wei.com>
Subject: [PATCH] f2fs: enhance to update i_mode and acl atomically in f2fs_setattr()

Previously, in f2fs_setattr(), we don't update S_ISUID|S_ISGID|S_ISVTX
bits with S_IRWXUGO bits and acl entries atomically, so in error path,
chmod() may partially success, this patch enhances to make chmod() flow
being atomical.

Signed-off-by: Chao Yu <yuchao0@...wei.com>
---
 fs/f2fs/acl.c   | 23 ++++++++++++++++++++++-
 fs/f2fs/file.c  |  7 ++++---
 fs/f2fs/xattr.c | 15 +++++++++------
 3 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index 1e5e9b1136ee..732ec10e7890 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -200,6 +200,27 @@ struct posix_acl *f2fs_get_acl(struct inode *inode, int type)
 	return __f2fs_get_acl(inode, type, NULL);
 }
 
+static int f2fs_acl_update_mode(struct inode *inode, umode_t *mode_p,
+			  struct posix_acl **acl)
+{
+	umode_t mode = inode->i_mode;
+	int error;
+
+	if (is_inode_flag_set(inode, FI_ACL_MODE))
+		mode = F2FS_I(inode)->i_acl_mode;
+
+	error = posix_acl_equiv_mode(*acl, &mode);
+	if (error < 0)
+		return error;
+	if (error == 0)
+		*acl = NULL;
+	if (!in_group_p(inode->i_gid) &&
+	    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
+		mode &= ~S_ISGID;
+	*mode_p = mode;
+	return 0;
+}
+
 static int __f2fs_set_acl(struct inode *inode, int type,
 			struct posix_acl *acl, struct page *ipage)
 {
@@ -213,7 +234,7 @@ static int __f2fs_set_acl(struct inode *inode, int type,
 	case ACL_TYPE_ACCESS:
 		name_index = F2FS_XATTR_INDEX_POSIX_ACL_ACCESS;
 		if (acl && !ipage) {
-			error = posix_acl_update_mode(inode, &mode, &acl);
+			error = f2fs_acl_update_mode(inode, &mode, &acl);
 			if (error)
 				return error;
 			set_acl_inode(inode, mode);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 596778f662fd..22a0101538c0 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -851,7 +851,6 @@ static void __setattr_copy(struct inode *inode, const struct iattr *attr)
 		if (!in_group_p(inode->i_gid) &&
 			!capable_wrt_inode_uidgid(inode, CAP_FSETID))
 			mode &= ~S_ISGID;
-		inode->i_mode = (inode->i_mode & S_IRWXUGO) | (mode & ~S_IRWXUGO);
 		set_acl_inode(inode, mode);
 	}
 }
@@ -951,8 +950,10 @@ int f2fs_setattr(struct dentry *dentry, struct iattr *attr)
 
 	if (attr->ia_valid & ATTR_MODE) {
 		err = posix_acl_chmod(inode, f2fs_get_inode_mode(inode));
-		if (err || is_inode_flag_set(inode, FI_ACL_MODE)) {
-			inode->i_mode = F2FS_I(inode)->i_acl_mode;
+
+		if (is_inode_flag_set(inode, FI_ACL_MODE)) {
+			if (!err)
+				inode->i_mode = F2FS_I(inode)->i_acl_mode;
 			clear_inode_flag(inode, FI_ACL_MODE);
 		}
 	}
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index 65afcc3cc68a..2086bef6c154 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -673,7 +673,7 @@ static int __f2fs_setxattr(struct inode *inode, int index,
 		}
 
 		if (value && f2fs_xattr_value_same(here, value, size))
-			goto exit;
+			goto same;
 	} else if ((flags & XATTR_REPLACE)) {
 		error = -ENODATA;
 		goto exit;
@@ -738,17 +738,20 @@ static int __f2fs_setxattr(struct inode *inode, int index,
 	if (error)
 		goto exit;
 
-	if (is_inode_flag_set(inode, FI_ACL_MODE)) {
-		inode->i_mode = F2FS_I(inode)->i_acl_mode;
-		inode->i_ctime = current_time(inode);
-		clear_inode_flag(inode, FI_ACL_MODE);
-	}
 	if (index == F2FS_XATTR_INDEX_ENCRYPTION &&
 			!strcmp(name, F2FS_XATTR_NAME_ENCRYPTION_CONTEXT))
 		f2fs_set_encrypted_inode(inode);
 	f2fs_mark_inode_dirty_sync(inode, true);
 	if (!error && S_ISDIR(inode->i_mode))
 		set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_CP);
+
+same:
+	if (is_inode_flag_set(inode, FI_ACL_MODE)) {
+		inode->i_mode = F2FS_I(inode)->i_acl_mode;
+		inode->i_ctime = current_time(inode);
+		clear_inode_flag(inode, FI_ACL_MODE);
+	}
+
 exit:
 	kfree(base_addr);
 	return error;
-- 
2.29.2

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