[PATCH] tmpfs: clear S_ISGID when setting posix ACLs

From: Gu Zheng
Date: Sun Jan 08 2017 - 20:35:50 EST


This change was missed the tmpfs modification in In CVE-2016-7097
commit 073931017b49 ("posix_acl: Clear SGID bit when setting
file permissions")
It can test by xfstest generic/375, which failed to clear
setgid bit in the following test case on tmpfs:

touch $testfile
chown 100:100 $testfile
chmod 2755 $testfile
_runas -u 100 -g 101 -- setfacl -m u::rwx,g::rwx,o::rwx $testfile

Signed-off-by: Gu Zheng <guzheng1@xxxxxxxxxx>
---
fs/posix_acl.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 5955220..d014dff 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -922,11 +922,10 @@ int simple_set_acl(struct inode *inode, struct posix_acl *acl, int type)
int error;

if (type == ACL_TYPE_ACCESS) {
- error = posix_acl_equiv_mode(acl, &inode->i_mode);
- if (error < 0)
- return 0;
- if (error == 0)
- acl = NULL;
+ error = posix_acl_update_mode(inode,
+ &inode->i_mode, &acl);
+ if (error)
+ return error;
}

inode->i_ctime = current_time(inode);
--
2.5.0