linux-ext4 - Re: [PATCH v2] f2fs: avoid utf8_strncasecmp() with unstable name

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Date:   Mon, 8 Jun 2020 09:37:52 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Eric Biggers <ebiggers@...nel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
CC:     <linux-ext4@...r.kernel.org>, Daniel Rosenberg <drosen@...gle.com>,
        <stable@...r.kernel.org>, Al Viro <viro@...iv.linux.org.uk>,
        <linux-fsdevel@...r.kernel.org>,
        Gabriel Krisman Bertazi <krisman@...labora.co.uk>
Subject: Re: [PATCH v2] f2fs: avoid utf8_strncasecmp() with unstable name

On 2020/6/2 4:08, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> If the dentry name passed to ->d_compare() fits in dentry::d_iname, then
> it may be concurrently modified by a rename.  This can cause undefined
> behavior (possibly out-of-bounds memory accesses or crashes) in
> utf8_strncasecmp(), since fs/unicode/ isn't written to handle strings
> that may be concurrently modified.
> 
> Fix this by first copying the filename to a stack buffer if needed.
> This way we get a stable snapshot of the filename.
> 
> Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups")
> Cc: <stable@...r.kernel.org> # v5.4+
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Daniel Rosenberg <drosen@...gle.com>
> Cc: Gabriel Krisman Bertazi <krisman@...labora.co.uk>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Reviewed-by: Chao Yu <yuchao0@...wei.com>

Thanks,