linux-kernel - Re: [PATCH] ufs: ensure fast symlinks are NUL-terminated

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Message-ID: <20081227122215.GA25619@rain>
Date:	Sat, 27 Dec 2008 15:22:15 +0300
From:	Evgeniy Dushistov <dushistov@...l.ru>
To:	Duane Griffin <duaneg@...da.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] ufs: ensure fast symlinks are NUL-terminated

On Tue, Dec 16, 2008 at 11:18:50PM +0000, Duane Griffin wrote:
> On Tue, Dec 16, 2008 at 10:40:55PM +0300, Evgeniy Dushistov wrote:
> > There is different types of ufs, one used 64 bit for "pointers to
> > blocks", another 32 bit,
> > so sizeof(UFS_I(inode)->i_u1.i_symlink))
> > is not right choice every time,
> > in ufs2 it should be
> > sizeof(UFS_I(inode)->i_u1.u2_i_data) which 2 times bigger,
> > 
> > also there is hint for *BSD ufs
> > 
> > fs/ufs/ufs_fs.h:
> > __fs32	fs_maxsymlinklen;/* max length of an internal symlink */
> > 
> > which may be used if ufs type ufs1 or ufs2
> 
> Hmm, I see. However it looks like ufs1_read_inode and ufs2_read_inode
> both copy the same, ((UFS_NDADDR + UFS_NINDIR) * 4), amount of inline
> symlink data. They also both copy it to ufs_inode_info->i_u1.i_symlink
> (not that that matters, I suppose). Perhaps I'm being obtuse, but it
> looks like inline ufs2 symlinks between 60 and 120 characters long are
> being truncated to 60 characters, no?
> 
> There also doesn't seem to be any validation of (f)s_maxsymlinklen being
> done. Unless I'm mistaken ufs_symlink could end up overwriting random
> memory if it contains a large bogus value.
> 
> Does that all sound correct? If so would you like me to whip up a couple
> of patches to fix it? I'll respin the NUL-termination patch on top of
> those, if so.
> 

Yes, it looks like there is typo in ufs2 variant of copying symlink names.
Typical value of superblock's maxsymlinklen field for ufs2 is 120.
Patches to fix this are welcome.

-- 
/Evgeniy

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