From: David Sterba <dsterba@suse.cz>
To: Jann Horn <jannh@google.com>
Cc: Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
David Sterba <dsterba@suse.com>,
Alex Lyakas <alex.bolshoy.btrfs@gmail.com>,
Alexander Block <ablock84@googlemail.com>,
linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH] btrfs: send: Ensure send_fd is writable
Date: Fri, 24 Nov 2023 18:43:56 +0100 [thread overview]
Message-ID: <20231124174356.GH18929@suse.cz> (raw)
In-Reply-To: <20231124164831.2191549-1-jannh@google.com>
On Fri, Nov 24, 2023 at 05:48:31PM +0100, Jann Horn wrote:
> kernel_write() requires the caller to ensure that the file is writable.
> Let's do that directly after looking up the ->send_fd.
>
> (We don't need a separate bailout path because the "out" path already
> does fput() if ->send_filp is non-NULL.)
>
> This has no security impact for two reasons:
>
> - the ioctl requires CAP_SYS_ADMIN
> - __kernel_write() bails out on read-only files - but only since 5.8,
> see commit a01ac27be472 ("fs: check FMODE_WRITE in __kernel_write")
>
> Reported-and-tested-by: syzbot+12e098239d20385264d3@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=12e098239d20385264d3
> Fixes: 31db9f7c23fb ("Btrfs: introduce BTRFS_IOC_SEND for btrfs send/receive")
> Cc: stable@vger.kernel.org
> Signed-off-by: Jann Horn <jannh@google.com>
Added to misc-next, thanks.
prev parent reply other threads:[~2023-11-24 17:51 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-24 16:48 [PATCH] btrfs: send: Ensure send_fd is writable Jann Horn
2023-11-24 17:43 ` David Sterba [this message]
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