4.9-stable review patch. If anyone has any objections, please let me know.
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From: "Eric W. Biederman" ebiederm@xmission.com
[ Upstream commit 75422726b0f717d67db3283c2eb5bc14fa2619c5 ]
Add MS_KERNMOUNT to the flags that are passed. Use sget_userns and force &init_user_ns instead of calling sget so that even if called from a weird context the internal filesystem will be considered to be in the intial user namespace.
Luis Ressel reported that the the failure to pass MS_KERNMOUNT into mount_pseudo broke his in development graphics driver that uses the generic drm infrastructure. I am not certain the deriver was bug free in it's usage of that infrastructure but since mount_pseudo_xattr can never be triggered by userspace it is clearer and less error prone, and less problematic for the code to be explicit.
Reported-by: Luis Ressel aranea@aixah.de Tested-by: Luis Ressel aranea@aixah.de Acked-by: Al Viro viro@ZenIV.linux.org.uk Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/libfs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/fs/libfs.c +++ b/fs/libfs.c @@ -245,7 +245,8 @@ struct dentry *mount_pseudo_xattr(struct struct inode *root; struct qstr d_name = QSTR_INIT(name, strlen(name));
- s = sget(fs_type, NULL, set_anon_super, MS_NOUSER, NULL); + s = sget_userns(fs_type, NULL, set_anon_super, MS_KERNMOUNT|MS_NOUSER, + &init_user_ns, NULL); if (IS_ERR(s)) return ERR_CAST(s);