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Date: Wed, 16 Oct 2013 12:56:33 +0800
From: Eryu Guan <guaneryu@gmail.com>
To: dsterba@suse.cz, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH] Btrfs-progs: check return value of realpath(3)
Message-ID: <20131016045633.GB11404@dhcp-13-216.nay.redhat.com>
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 <20131015164941.GL5787@twin.jikos.cz>
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On Tue, Oct 15, 2013 at 06:49:41PM +0200, David Sterba wrote:
> On Sat, Oct 12, 2013 at 11:47:52PM +0800, Eryu Guan wrote:
> > I hit a segfault when deleting a subvolume with very long name(>4096),
> 
> How do you get a valid pathname longer than PATH_MAX which is 4096 ?

Just as the steps in reproducer, you can try the following

path=/mnt/btrfs
for i in `seq 1 381`;do
	path="$path/subvol_$i"
	btrfs sub create $path
done
echo ${#path}  # len is 4093 here

((i++))
path="$path/subvol_$i"
btrfs sub create $path
echo ${#path}  # The length of absolute path of this subvolume is greater than 4096 now

Maybe just another bug of btrfs-progs?
> 
> > Fix it by checking return value of realpath(3), also fix the one in
> > find_mount_root().
> 
> The error handling itself is ok.

Thanks for the review!

Eryu