linux-ext4 - Re: [PATCH] filefrag: handle invalid st

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Message-ID: <YAe1EYzFWWxAK2I/@mit.edu>
Date:   Tue, 19 Jan 2021 23:44:01 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     Luis Henriques <lhenriques@...e.de>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH] filefrag: handle invalid st_dev and blksize cases

On Wed, Oct 28, 2020 at 03:55:50PM +0000, Luis Henriques wrote:
> It is possible to crash filefrag with a "Floating point exception" in
> two different scenarios:
> 
> 1. When fstat() returns a device ID set to 0
> 2. When FIGETBSZ ioctl returns a blocksize of 0
> 
> In both scenarios a divide-by-zero will occur in frag_report() because
> variable blksize will be set to zero.
> 
> I've managed to trigger this crash with an old CephFS kernel client,
> using xfstest generic/519.  The first scenario has been fixed by kernel
> commit 75c9627efb72 ("ceph: map snapid to anonymous bdev ID").  The
> second scenario is also fixed with commit 8f97d1e99149 ("vfs: fix
> FIGETBSZ ioctl on an overlayfs file").
> 
> However, it is desirable to handle these two scenarios gracefully by
> checking these conditions explicitly.
> 
> Signed-off-by: Luis Henriques <lhenriques@...e.de>

Thanks, applied.

					- Ted