linux-kernel - Re: [PATCH][V2] EDAC/i10nm: shift exponent is negative

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Date:   Tue, 4 Jul 2023 15:02:23 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     Koba Ko <koba.ko@...onical.com>
Cc:     Borislav Petkov <bp@...en8.de>, Tony Luck <tony.luck@...el.com>,
        James Morse <james.morse@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Robert Richter <rric@...nel.org>, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][V2] EDAC/i10nm: shift exponent is negative

Here is a better commit message.  You can just copy and paste it.
------------------------------------------
[PATCH v3] EDAC/i10nm: Prevent negative shifts in skx_get_dimm_info().

UBSAN generated the following warning during a timeout:

    UBSAN: shift-out-of-bounds in drivers/edac/skx_common.c:369:16
    shift exponent -66 is negative

That most likely means that rows, cols, and ranks were all set to
-EINVAL.  Address this in two ways.

1) Change the debug output in skx_get_dimm_attr() to KERN_ERR so that
   users will know where exactly the error is.
2) Add a check for errors in skx_get_dimm_info().

Fixes: 88a242c98740 ("EDAC, skx_common: Separate common code out from skx_edac")
Signed-off-by:
-----------------------------------------------

> @@ -351,6 +351,8 @@ int skx_get_dimm_info(u32 mtr, u32 mcmtr, u32 amap, struct dimm_info *dimm,
>  	ranks = numrank(mtr);
>  	rows = numrow(mtr);
>  	cols = imc->hbm_mc ? 6 : numcol(mtr);
> +	if (ranks == -EINVAL || rows == -EINVAL || cols == -EINVAL)
> +		return 0;

Change this to:

	if (rangks < 0 || rows < 0 || cols < 0)
		return 0;

It's bad form to check for a specific error code unless there is a need.

regards,
dan carpenter