From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E0A02222AA; Fri, 4 Sep 2026 09:01:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788512472; cv=none; b=Fj83OEeStL/dnA0zuY0CXBVCn2uC2SvvSl3sCpUDSFb2hvnTwxg/BXWxKbwNTLIKYMbbJGaRpykfXLxKiskzGs5J3nU++ACBQzimla3Q2OYWkt6LBF8jjaem7soinCNduBQN0N5pLKaXvfaOd8D/P+NlNNScYlTLMk2ToPbS7w8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788512472; c=relaxed/simple; bh=NKQFYA/36+trZ8mR4+iGgQHvRrS7dZWgZnNZFkrK40M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DIEc97JufsSf/k8mIHgS6k+ThYDu/hFEueVTYkMkasobSBPK1tQekw5vNlfe0Oyyz1w/IyXD5kCPtOpfE1E8iVFVk7yW5E7VpE+0s1jvGWo64UV94IX+G2Pgbh9UrByJ99lk9RvEe3iqNXDpNuvxlO7swAelsHFcrAQhjp6ObP4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JH8R3oTh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JH8R3oTh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D03841F00A3D; Fri, 4 Sep 2026 09:01:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788512471; bh=NS43r1NlPHoz3Menx8qLeACzHNPCiAWFDDBQZ2Ncqlo=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=JH8R3oThTjf7VbgyDYAPuSERILexkhuy68q6S1R/j3k/xU/SQ6pKR3M2STiVCtoHB N4HPsS8DQBcHTVMRDKMixaJfZj6KsdUi6flqlVHchSUh+EefEVewz6t6s7WtAMBOeJ Ne/DDRDYmPRQsrF1gzDzU68tIP+YLcuaGzUbmyY3aIASIqIJ4ih/2x0Z8NuR9CSIMx DbsFfSOtbOWzQP6VioFxiuQ4PjtSlyVmMco+ejyW09TzSDfxc5DIUggo2qelo+xcr6 EPF7LjD5kV6at2CbWtfaDYmAXt1icNVl+5k3xYCyClty41Zpigub4q/rajGOS10E/r a2YCLFTlvAlIw== Message-ID: <497a85d3-e062-4930-bcb8-c86a8205e7b2@kernel.org> Date: Fri, 4 Sep 2026 11:01:04 +0200 Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/5] slab: handle ERR_PTR values in kfree and hardened usercopy Content-Language: en-US To: Karl Mehltretter , Harry Yoo , Andrew Morton Cc: Rasmus Villemoes , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Catalin Marinas , Kees Cook , "Gustavo A . R . Silva" , Arnd Bergmann , Greg Kroah-Hartman , Shuah Khan , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-hardening@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev References: <20260903203720.63689-1-kmehltretter@gmail.com> <20260903203720.63689-4-kmehltretter@gmail.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260903203720.63689-4-kmehltretter@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/3/26 22:37, Karl Mehltretter wrote: > Passing an ERR_PTR to kfree() currently reaches virt_to_page() and may > fault. Warn and return instead, leaving the bad caller visible without > using the pointer as allocator metadata. > > Also reject ERR_PTR values in hardened usercopy. Keep both checks > separate from ZERO_OR_NULL_PTR(), whose exact matching is required by > krealloc(). > > Link: https://lore.kernel.org/r/CAG48ez05QVn6_gQ2TBrRa1a_DWQoaSSYubUsu5YMWxx-gqMijQ@mail.gmail.com > Link: https://lore.kernel.org/r/202608111716.0FA9DB17@keescook > Link: https://github.com/KSPP/linux/issues/93 > Assisted-by: LLM > Signed-off-by: Karl Mehltretter > --- > mm/slub.c | 3 +++ > mm/usercopy.c | 3 +++ > 2 files changed, 6 insertions(+) > > diff --git a/mm/slub.c b/mm/slub.c > index f9b56cb439e7..027b44dd7f07 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -6780,6 +6780,9 @@ void kfree(const void *object) > if (unlikely(ZERO_OR_NULL_PTR(object))) > return; > > + if (WARN_ON(IS_ERR(object))) Wonder if WARN_ON_ONCE() would be better. Also wonder about the benefits for hardening (as opposed to debugging). Without this check it would fault. Now it warns, but hardened setups often use panic_on_warn anyway, so the result is the same? > + return; > + > page = virt_to_page(object); > slab = page_slab(page); > if (!slab) { > diff --git a/mm/usercopy.c b/mm/usercopy.c > index 5de7a518b1b1..c8d8703544c6 100644 > --- a/mm/usercopy.c > +++ b/mm/usercopy.c > @@ -157,6 +157,9 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, > /* Reject if NULL or ZERO-allocation. */ > if (ZERO_OR_NULL_PTR(ptr)) > usercopy_abort("null address", NULL, to_user, ptr, n); > + > + if (IS_ERR_VALUE(ptr)) > + usercopy_abort("ERR_PTR", NULL, to_user, ptr, n); > } > > static inline void check_heap_object(const void *ptr, unsigned long n,