diff options
author | Jan Kara <jack@suse.cz> | 2016-12-14 13:24:50 +0100 |
---|---|---|
committer | Sasha Levin <alexander.levin@verizon.com> | 2016-12-23 08:56:35 -0500 |
commit | 62fa696b7b435e93ed114dd6a23aa0881d7f81b9 (patch) | |
tree | b79fe7082c8370a323a83b947804d7340c823f35 /fs/posix_acl.c | |
parent | de42b9559d0c540152260d484dbc70b3e81f8738 (diff) |
posix_acl: Clear SGID bit when setting file permissions
[ Upstream commit 073931017b49d9458aa351605b43a7e34598caef ]
When file permissions are modified via chmod(2) and the user is not in
the owning group or capable of CAP_FSETID, the setgid bit is cleared in
inode_change_ok(). Setting a POSIX ACL via setxattr(2) sets the file
permissions as well as the new ACL, but doesn't clear the setgid bit in
a similar way; this allows to bypass the check in chmod(2). Fix that.
References: CVE-2016-7097
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Philipp Hahn <hahn@univention.de>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Diffstat (limited to 'fs/posix_acl.c')
-rw-r--r-- | fs/posix_acl.c | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/fs/posix_acl.c b/fs/posix_acl.c index a9dafa83678c..0ef1c3722504 100644 --- a/fs/posix_acl.c +++ b/fs/posix_acl.c @@ -598,6 +598,37 @@ no_mem: } EXPORT_SYMBOL_GPL(posix_acl_create); +/** + * posix_acl_update_mode - update mode in set_acl + * + * Update the file mode when setting an ACL: compute the new file permission + * bits based on the ACL. In addition, if the ACL is equivalent to the new + * file mode, set *acl to NULL to indicate that no ACL should be set. + * + * As with chmod, clear the setgit bit if the caller is not in the owning group + * or capable of CAP_FSETID (see inode_change_ok). + * + * Called from set_acl inode operations. + */ +int posix_acl_update_mode(struct inode *inode, umode_t *mode_p, + struct posix_acl **acl) +{ + umode_t mode = inode->i_mode; + int error; + + 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; +} +EXPORT_SYMBOL(posix_acl_update_mode); + /* * Fix up the uids and gids in posix acl extended attributes in place. */ |