From: Miklos Szeredi Date: Tue, 6 Dec 2016 15:18:45 +0000 (+0100) Subject: fuse: fix clearing suid, sgid for chown() X-Git-Tag: v3.2.85~27 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=6d1f19c6c03cc1a2c6b8862a411db88d70f4e697;ds=sidebyside fuse: fix clearing suid, sgid for chown() commit c01638f5d919728f565bf8b5e0a6a159642df0d9 upstream. 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") Reviewed-by: Jeff Layton [bwh: Backported to 3.2: adjust context, indentation] Signed-off-by: Ben Hutchings --- diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 4041f76dd6c4..d0f57b18c01c 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1398,8 +1398,6 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr) int ret; if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) { - int kill; - attr->ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_MODE); /* @@ -1411,12 +1409,11 @@ 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; }