From c01638f5d919728f565bf8b5e0a6a159642df0d9 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Tue, 6 Dec 2016 16:18:45 +0100 Subject: fuse: fix clearing suid, sgid for chown() Basically, the pjdfstests set the ownership of a file to 06555, and then chowns it (as root) to a new uid/gid. Prior to commit a09f99eddef4 ("fuse: fix killing s[ug]id in setattr"), fuse would send down a setattr with both the uid/gid change and a new mode. Now, it just sends down the uid/gid change. Technically this is NOTABUG, since POSIX doesn't _require_ that we clear these bits for a privileged process, but Linux (wisely) has done that and I think we don't want to change that behavior here. This is caused by the use of should_remove_suid(), which will always return 0 when the process has CAP_FSETID. In fact we really don't need to be calling should_remove_suid() at all, since we've already been indicated that we should remove the suid, we just don't want to use a (very) stale mode for that. This patch should fix the above as well as simplify the logic. Reported-by: Jeff Layton Signed-off-by: Miklos Szeredi Fixes: a09f99eddef4 ("fuse: fix killing s[ug]id in setattr") Cc: Reviewed-by: Jeff Layton --- fs/fuse/dir.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) (limited to 'fs/fuse/dir.c') diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index b3ebe512d64c..096f79997f75 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1739,8 +1739,6 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr) * This should be done on write(), truncate() and chown(). */ if (!fc->handle_killpriv) { - int kill; - /* * ia_mode calculation may have used stale i_mode. * Refresh and recalculate. @@ -1750,12 +1748,11 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr) return ret; attr->ia_mode = inode->i_mode; - kill = should_remove_suid(entry); - if (kill & ATTR_KILL_SUID) { + if (inode->i_mode & S_ISUID) { attr->ia_valid |= ATTR_MODE; attr->ia_mode &= ~S_ISUID; } - if (kill & ATTR_KILL_SGID) { + if ((inode->i_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { attr->ia_valid |= ATTR_MODE; attr->ia_mode &= ~S_ISGID; } -- cgit v1.2.3