linux-kernel - Re: [PATCH v2 1/8] unicode: Fix utf8

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Message-ID: <20240903114034.GC1002375@mit.edu>
Date: Tue, 3 Sep 2024 07:40:34 -0400
From: "Theodore Ts'o" <tytso@....edu>
To: André Almeida <andrealmeid@...lia.com>
Cc: Hugh Dickins <hughd@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        krisman@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, kernel-dev@...lia.com,
        Daniel Rosenberg <drosen@...gle.com>, smcv@...labora.com,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 1/8] unicode: Fix utf8_load() error path

On Mon, Sep 02, 2024 at 07:55:03PM -0300, André Almeida wrote:
> utf8_load() requests the symbol "utf8_data_table" and then checks if the
> requested UTF-8 version is supported. If it's unsupported, it tries to
> put the data table using symbol_put(). If an unsupported version is
> requested, symbol_put() fails like this:
> 
>  kernel BUG at kernel/module/main.c:786!
>  RIP: 0010:__symbol_put+0x93/0xb0
>  Call Trace:
>   <TASK>
>   ? __die_body.cold+0x19/0x27
>   ? die+0x2e/0x50
>   ? do_trap+0xca/0x110
>   ? do_error_trap+0x65/0x80
>   ? __symbol_put+0x93/0xb0
>   ? exc_invalid_op+0x51/0x70
>   ? __symbol_put+0x93/0xb0
>   ? asm_exc_invalid_op+0x1a/0x20
>   ? __pfx_cmp_name+0x10/0x10
>   ? __symbol_put+0x93/0xb0
>   ? __symbol_put+0x62/0xb0
>   utf8_load+0xf8/0x150
> 
> That happens because symbol_put() expects the unique string that
> identify the symbol, instead of a pointer to the loaded symbol. Fix that
> by using such string.
> 
> Fixes: 2b3d04787012 ("unicode: Add utf8-data module")
> Signed-off-by: André Almeida <andrealmeid@...lia.com>

Nice catch!

Reviewed-by: Theodore Ts'o <tytso@....edu>