From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frank Rowand Subject: Re: [PATCH] of: overlay: Fix uninitialized vars in dup_and_fixup_symbol_prop() Date: Tue, 19 Sep 2017 17:20:53 -0700 Message-ID: <59C1B465.1010209@gmail.com> References: <1505039164-25468-1-git-send-email-geert@linux-m68k.org> <59C16197.4040403@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Geert Uytterhoeven Cc: Pantelis Antoniou , Rob Herring , Grant Likely , Arnd Bergmann , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org On 09/19/17 13:16, Geert Uytterhoeven wrote: > Hi Frank, > > On Tue, Sep 19, 2017 at 8:27 PM, Frank Rowand wrote: >> On 09/10/17 03:26, Geert Uytterhoeven wrote: >>> With gcc 4.1.2: >>> >>> drivers/of/overlay.c: In function ‘dup_and_fixup_symbol_prop’: >>> drivers/of/overlay.c:108: warning: ‘overlay_name_len’ may be used uninitialized in this function >>> drivers/of/overlay.c:100: warning: ‘ovinfo’ may be used uninitialized in this function >>> >>> Indeed, if ov->count == 0, both variables are uninitialized, which may >>> lead to a crash when dereferencing ovinfo later. >>> >>> Currently this is a false positive, as the sole creator of of_overlay >>> structures (of_build_overlay_info(), introduced in commit >>> 7518b5890d8ac366 ("of/overlay: Introduce DT overlay support") checks for >>> this. >>> >>> To prevent future issues, add a check for a zero ov->count to >>> dup_and_fixup_symbol_prop(). Note that this does not get rid of the >>> actual compiler warning. >>> >>> Fixes: d1651b03c2df75db ("of: overlay: add overlay symbols to live device tree") >>> Signed-off-by: Geert Uytterhoeven >>> --- >>> drivers/of/overlay.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c >>> index 8ecfee31ab6d3874..ebe19e0f8e4d1f4b 100644 >>> --- a/drivers/of/overlay.c >>> +++ b/drivers/of/overlay.c >>> @@ -108,7 +108,7 @@ static struct property *dup_and_fixup_symbol_prop(struct of_overlay *ov, >>> int overlay_name_len; >>> int target_path_len; >>> >>> - if (!prop->value) >>> + if (!ov->count || !prop->value) >>> return NULL; >>> symbol_path = prop->value; >>> >> >> I did not see this patch due to an overzealous spam filter. I noticed it >> when Rob replied with his applied email. >> >> This check is not needed to prevent accessing overlay_name_len and ovinfo >> when ov->count == 0. That is already prevented by: >> >> if (k >= ov->count) >> goto err_free; >> >> because k will be zero and ov->count will be zero. > > Thank you, I stand corrected. No problem. It's not real obvious, you really need to stop and ponder. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html