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 08:35:46 -0600 [thread overview]
Message-ID: <ZeXcQmHWcYvfCR93@do-x1extreme> (raw)
In-Reply-To: <20240304-zeitschrift-tagung-6f2a28e781bc@brauner>
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.
> 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.
next prev parent reply other threads:[~2024-03-04 14:35 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 [this message]
2024-03-04 14:44 ` Seth Forshee
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