From fea6d2a610c899bb7fd8e95fcbf46900b886e5a3 Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Mon, 13 Feb 2017 15:45:26 -0500 Subject: [PATCH] vfs: Use upper filesystem inode in bprm_fill_uid() Right now bprm_fill_uid() uses inode fetched from file_inode(bprm->file). This in turn returns inode of lower filesystem (in a stacked filesystem setup). I was playing with modified patches of shiftfs posted by james bottomley and realized that through shiftfs setuid bit does not take effect. And reason being that we fetch uid/gid from inode of lower fs (and not from shiftfs inode). And that results in following checks failing. /* We ignore suid/sgid if there are no mappings for them in the ns */ if (!kuid_has_mapping(bprm->cred->user_ns, uid) || !kgid_has_mapping(bprm->cred->user_ns, gid)) return; uid/gid fetched from lower fs inode might not be mapped inside the user namespace of container. So we need to look at uid/gid fetched from upper filesystem (shiftfs in this particular case) and these should be mapped and setuid bit can take affect. Signed-off-by: Vivek Goyal Signed-off-by: Eric W. Biederman --- fs/exec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/exec.c b/fs/exec.c index c195ebb8e2aa..698a86094f76 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1475,7 +1475,7 @@ static void bprm_fill_uid(struct linux_binprm *bprm) if (task_no_new_privs(current)) return; - inode = file_inode(bprm->file); + inode = bprm->file->f_path.dentry->d_inode; mode = READ_ONCE(inode->i_mode); if (!(mode & (S_ISUID|S_ISGID))) return; -- 2.20.1