linux-kernel - Re: [PATCH v2 1/7] kdb: Fix buffer overflow during tab-complete

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Message-ID: <CAD=FV=VrOSN8VFaRwH-k4wCLm6Xb=zJyozJac+ijzhDvH8BYxA@mail.gmail.com>
Date: Mon, 22 Apr 2024 16:51:49 -0700
From: Doug Anderson <dianders@...omium.org>
To: Daniel Thompson <daniel.thompson@...aro.org>
Cc: Jason Wessel <jason.wessel@...driver.com>, kgdb-bugreport@...ts.sourceforge.net, 
	linux-kernel@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>, 
	stable@...r.kernel.org
Subject: Re: [PATCH v2 1/7] kdb: Fix buffer overflow during tab-complete

Hi,

On Mon, Apr 22, 2024 at 9:37 AM Daniel Thompson
<daniel.thompson@...aro.org> wrote:
>
> Currently, when the user attempts symbol completion with the Tab key, kdb
> will use strncpy() to insert the completed symbol into the command buffer.
> Unfortunately it passes the size of the source buffer rather than the
> destination to strncpy() with predictably horrible results. Most obviously
> if the command buffer is already full but cp, the cursor position, is in
> the middle of the buffer, then we will write past the end of the supplied
> buffer.
>
> Fix this by replacing the dubious strncpy() calls with memmove()/memcpy()
> calls plus explicit boundary checks to make sure we have enough space
> before we start moving characters around.
>
> Reported-by: Justin Stitt <justinstitt@...gle.com>
> Closes: https://lore.kernel.org/all/CAFhGd8qESuuifuHsNjFPR-Va3P80bxrw+LqvC8deA8GziUJLpw@mail.gmail.com/
> Cc: stable@...r.kernel.org
> Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
> ---
>  kernel/debug/kdb/kdb_io.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)

Boy, this function (and especially the tab handling) is hard to read.
I spent a bit of time trying to grok it and, as far as I can tell,
your patch makes things better and I don't see any bugs.

Reviewed-by: Douglas Anderson <dianders@...omium.org>