Fixes: 036d523641c6 ("vfs: Don't create inodes with a uid or gid unknown
to the vfs")
This fixes the bugzilla bug #183461
(https://bugzilla.kernel.org/show_bug.cgi?id=183461) "mkdir(2) returns
EOVERFLOW on tmpfs in user namespace" that was introduced in the
aforementioned commit.
Since filesystems with the FS_USERNS_MOUNT flag (mainly tmpfs in this
case) are safe to use within user namespaces they should be allowed
to create inodes without checking whether their uid and gid has a
mapping or not.
I learned most of what I know about user namespaces while researching
this bug, so there's a fair chance that I've misunderstood something.
Feedback is greatly appreciated.
Signed-off-by: Johanna Abrahamsson <johanna@xxxxxxxx>
---
fs/namei.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 1669c93d..9e45e01 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2816,10 +2816,12 @@ static inline int may_create(struct inode *dir, struct dentry *child)
return -EEXIST;
if (IS_DEADDIR(dir))
return -ENOENT;
- s_user_ns = dir->i_sb->s_user_ns;
- if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
- !kgid_has_mapping(s_user_ns, current_fsgid()))
- return -EOVERFLOW;
+ if (!(dir->i_sb->s_type->fs_flags & FS_USERNS_MOUNT)) {
+ s_user_ns = dir->i_sb->s_user_ns;
+ if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
+ !kgid_has_mapping(s_user_ns, current_fsgid()))
+ return -EOVERFLOW;
+ }
return inode_permission(dir, MAY_WRITE | MAY_EXEC);
}
--
2.1.4
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