On Fri, Mar 20, 2015 at 10:28:31AM -0400, Andrew W Elble wrote:
>
> Any update/feedback?
If you haven't already: could you resend it, To: Al, and a "Cc:
stable@xxxxxxxxxxxxxxx" line?
--b.
>
> "J. Bruce Fields" <bfields@xxxxxxxxxxxx> writes:
>
> > Looks OK to me. I think it would go through Al.--b.
> >
> > Acked-by: J. Bruce Fields <bfields@xxxxxxxxxx>
> >
> > On Mon, Feb 23, 2015 at 08:51:24AM -0500, Andrew Elble wrote:
> >> We have observed a BUG() crash in fs/attr.c:notify_change(). The crash
> >> occurs during an rsync into a filesystem that is exported via NFS.
> >>
> >> 1.) fs/attr.c:notify_change() modifies the caller's version of attr.
> >> 2.) 6de0ec00ba8d ("VFS: make notify_change pass ATTR_KILL_S*ID to
> >> setattr operations") introduced a BUG() restriction such that "no
> >> function will ever call notify_change() with both ATTR_MODE and
> >> ATTR_KILL_S*ID set". Under some circumstances though, it will have
> >> assisted in setting the caller's version of attr to this very
> >> combination.
> >> 3.) 27ac0ffeac80 ("locks: break delegations on any attribute
> >> modification") introduced code to handle breaking
> >> delegations. This can result in notify_change() being re-called. attr
> >> _must_ be explicitly reset to avoid triggering the BUG() established
> >> in #2.
> >> 4.) The path that that triggers this is via fs/open.c:chmod_common().
> >> The combination of attr flags set here and in the first call to
> >> notify_change() along with a later failed break_deleg_wait()
> >> results in notify_change() being called again via retry_deleg
> >> without resetting attr.
> >>
> >> Solution is to move retry_deleg in chmod_common() a bit further up to
> >> ensure attr is completely reset.
> >>
> >> There are other places where this seemingly could occur, such as
> >> fs/utimes.c:utimes_common(), but the attr flags are not initially
> >> set in such a way to trigger this.
> >>
> >> Fixes: 27ac0ffeac80 ("locks: break delegations on any attribute modification")
> >> Reported-by: Eric Meddaugh <etmsys@xxxxxxx>
> >> Tested-by: Eric Meddaugh <etmsys@xxxxxxx>
> >> Signed-off-by: Andrew Elble <aweits@xxxxxxx>
> >> ---
> >> fs/open.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/fs/open.c b/fs/open.c
> >> index 33f9cbf2610b..44a3be145bfe 100644
> >> --- a/fs/open.c
> >> +++ b/fs/open.c
> >> @@ -570,6 +570,7 @@ static int chown_common(struct path *path, uid_t user, gid_t group)
> >> uid = make_kuid(current_user_ns(), user);
> >> gid = make_kgid(current_user_ns(), group);
> >>
> >> +retry_deleg:
> >> newattrs.ia_valid = ATTR_CTIME;
> >> if (user != (uid_t) -1) {
> >> if (!uid_valid(uid))
> >> @@ -586,7 +587,6 @@ static int chown_common(struct path *path, uid_t user, gid_t group)
> >> if (!S_ISDIR(inode->i_mode))
> >> newattrs.ia_valid |=
> >> ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
> >> -retry_deleg:
> >> mutex_lock(&inode->i_mutex);
> >> error = security_path_chown(path, uid, gid);
> >> if (!error)
> >> --
> >> 1.9.2
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> >> the body of a message to majordomo@xxxxxxxxxxxxxxx
> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
>
> --
> Andrew W. Elble
> aweits@xxxxxxxxxxxxxxxxxx
> Infrastructure Engineer, Communications Technical Lead
> Rochester Institute of Technology
> PGP: BFAD 8461 4CCF DC95 DA2C B0EB 965B 082E 863E C912
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