From: Seth Forshee <sforshee@kernel.org>
To: Christian Brauner <brauner@kernel.org>
Cc: Christian Schoenebeck <linux_oss@crudebyte.com>,
Eric Van Hensbergen <ericvh@kernel.org>,
Latchesar Ionkov <lucho@ionkov.net>,
Dominique Martinet <asmadeus@codewreck.org>,
v9fs@lists.linux.dev, linux-kernel@vger.kernel.org,
xingwei lee <xrivendell7@gmail.com>,
sam sun <samsun1006219@gmail.com>
Subject: Re: [PATCH] 9p: cap xattr max size to XATTR_SIZE_MAX
Date: Mon, 4 Mar 2024 08:44:23 -0600 [thread overview]
Message-ID: <ZeXeR+2f/ozdamWL@do-x1extreme> (raw)
In-Reply-To: <ZeXcQmHWcYvfCR93@do-x1extreme>
On Mon, Mar 04, 2024 at 08:35:46AM -0600, Seth Forshee wrote:
> On Mon, Mar 04, 2024 at 03:19:58PM +0100, Christian Brauner wrote:
> > On Mon, Mar 04, 2024 at 02:35:07PM +0100, Christian Schoenebeck wrote:
> > > On Monday, March 4, 2024 1:42:43 PM CET Dominique Martinet wrote:
> > > > We probably shouldn't ever get an xattr bigger than that, and the current check
> > > > of SSIZE_MAX is a bit too large.
> > >
> > > Maybe, OTOH e.g. ACLs (dynamic size) are implemented by storing them as xattrs
> > > on 9p server as well, and this change somewhat expects server to run Linux as
> > > well. So maybe s/XATTR_SIZE_MAX/KMALLOC_MAX_SIZE/ might be more appropriate,
> > > considering that this patch is about fixing a potential kmalloc() warning?
> > >
> > > Worth to mention in the commit log BTW what the issue was.
> > >
> > > /Christian
> >
> > So the error is somewhat specific to filesystem capabilities which also
> > live in the xattr apis but Seth is working to get rid of them in there.
> >
> > They currently use a special api vfs_getxattr_alloc() which is an
> > in-kernel api that does a racy query-size+allocate-buffer+retrieve-data
> > dance.
>
> Yes, the patches I've sent does use vfs_getxattr_alloc() for fscaps
> anymore.
Sorry, typo above. My patches do _not_ use vfs_getxattr_alloc() for
fscaps anymore.
>
> > That api is used for fscaps, security labels, and other xattrs. And that
> > api doesn't do any size checks which probably should also be fixed now
> > that I write this.
> >
> > @Seth?
>
> I agree. I don't see any reason that vfs_getxattr_alloc() shouldn't just
> bail out with an error if the size of the xattr is >= XATTR_SIZE_MAX.
prev parent reply other threads:[~2024-03-04 14:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-04 12:42 [PATCH] 9p: cap xattr max size to XATTR_SIZE_MAX Dominique Martinet
2024-03-04 13:35 ` Christian Schoenebeck
2024-03-04 14:19 ` Christian Brauner
2024-03-04 14:35 ` Seth Forshee
2024-03-04 14:44 ` Seth Forshee [this message]
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