[PATCH] f2fs: enhance to update i_mode and acl atomically in f2fs_setattr()

From: Chao Yu
Date: Fri Dec 25 2020 - 03:53:48 EST


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@xxxxxxxxxx>
---
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