linux-kernel - Re: WARNING in __kernel

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Message-ID: <202110061510.24208C2@keescook>
Date:   Wed, 6 Oct 2021 15:10:43 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Theodore Ts'o <tytso@....edu>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Hao Sun <sunhao.th@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
        Christoph Hellwig <hch@....de>
Subject: Re: WARNING in __kernel_read

On Wed, Oct 06, 2021 at 09:57:22AM -0400, Theodore Ts'o wrote:
> On Wed, Oct 06, 2021 at 01:17:32PM +0100, Matthew Wilcox wrote:
> > finit_module() is not the only caller of kernel_read_file_from_fd()
> > which passes it a fd that userspace passed in, for example
> > kexec_file_load() doesn't validate the fd either.  We could validate
> > the fd in individual syscalls, in kernel_read_file_from_fd()
> > or just do what vfs_read() does and return -EBADF without warning.
> 
> My suggestion would be to do both, and keep a WARN() in
> __kernel_read(), since that should never happen (and we want a stack
> trace if it does).

Agreed.

-- 
Kees Cook