From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794389898; b=XIVLSPljQLVzo23NOHJ78iHPJbSrrXGx+6EFXfswcBYFQxSmRy68yKsR20wmkn1CepbF B9u4QRxFKt1F3PWrJTQByLz66hP7dw4hzLX3d2duhy5QFFOn6NbYjywsNIvnLIa2Ixll2 l6HxMfS8Jwubh3LsOOmxEC9wwbnxntD33sqvuiX7k5uYgDgQ0o+tUzP/AZ7hw5FnYieK7 s52LDlTjpGyV9ss3fC8dC3z5XZckdQfSCrLRnhuh0K7yMUrewjtTjtjT7vLTt7it4vK/e rUWI52ly39+1ZO1mGgVWkgGN3cQJN9ikuMEXWUg/HyNj5ivoWK0OAUC8frwzkAwnuZg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794389898; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:Content-Language:To:Cc:References:From:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=5p/q3+WMS3ls8L+KObTnHmV8zpLfczVrwuNUj9yKsvQ=; b=fP/co/ghCsXlUg+HytqaH1IoVg9MBAT6CRW32g9IWJpWSYxC3tCVz8fa5G/Lzk7EwwMH hkHWhGKhwEZQCPIykKdx+D9hJnoop3dYppEeG0d4gSEVyjwv/AwV5soGZR7XXRzCSNABm l1LT+sPLUzcsVyHB91QQBNlOPbDRlS8lZLSKVFECIpHMOca3Aeta+G7vqyEcwvOmq5b6D 9y0u7gV5ZjGWtH2lNQu3B46UwIY6vzGVJkQmFznXU1BItUGvd1aauYQ+Tp1DzmZrrj52J fRssma/8hbpRQX7Ysig03Zub13T8AliBTBn4qlHAvgFOk6ahO/LFjWjbKM6+mZnCPNw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=MzR37AmC; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 60AA6606A327 for ; Wed, 11 Nov 2026 09:38:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=MzR37AmC Received: by smtp.kernel.org (Postfix) with ESMTPSA id D79D91F00A06; Wed, 11 Nov 2026 09:38:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794389898; bh=5p/q3+WMS3ls8L+KObTnHmV8zpLfczVrwuNUj9yKsvQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=MzR37AmCszwGbQH+6B0ZwpFLoz/cN8Un+xeXNMhovJUZ/SghyRwpY2NP1NfcnmXLh slCIxDons0PwXhP6IQbO5Q+NTv+dwJmdtafsQhv2LJQ9yRoNir8jp7il4Q8ob368ZI 9aiFYwL7b6Dy+Y4PfoVdvMIXAAZ9S53m/5DbrpZAEYZeAH0iBM+ofGCE5N6uY1b+wt tnZCwTuG0BiN8pCnOH1DCNxPAT3lpCsEWgr8aoFBUVwOFbf4k+ewGTBFkTXceIRyTk HZGac6UXuQfiCFRdcaCaEH3h8VpZjBmmr5tcc9D7AH0v8kK2vEsSfWudNIVhE3njf0 mOnTOJOWiAVRQ== Message-ID: Date: Wed, 11 Nov 2026 10:38:15 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] mm: only assert VMA locks if CONFIG_DEBUG_VM is set Content-Language: en-US To: "Lorenzo Stoakes (ARM)" , Andrew Morton , Suren Baghdasaryan , "Liam R. Howlett" , Shakeel Butt Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261110-tame-vma-asserts-v1-0-be293ff499a7@kernel.org> <20261110-tame-vma-asserts-v1-2-be293ff499a7@kernel.org> 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: <20261110-tame-vma-asserts-v1-2-be293ff499a7@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/10/26 17:57, Lorenzo Stoakes (ARM) wrote: > Similar to the mmap lock asserts, we have also asserted VMA locks > regardless of whether or not the kernel is a debug build or not. > > Similarly, these are asserting basic assumptions about kernel code which > should never assert in production code. > > Since all such bugs are generally asserted using VM_WARN_ON_ONCE() or > similar, it creates an odd and inconsistent situation where some > programmatic asserts are only checked under CONFIG_DEBUG_VM and some are > always checked. > > Since the intent is the same as any VM_WARN_ON_ONCE() check, do not assert > if CONFIG_DEBUG_VM is not set. > > Implement by updating vma_assert_attached() and vma_assert_detached() to > use VM_WARN_ON_ONCE() rather than WARN_ON_ONCE(), and gating > vma_assert_[write_]locked() and vma_assert_can_modify() on CONFIG_DEBUG_VM. > > nommu loses its CONFIG_LOCKDEP asserts if !CONFIG_DEBUG_VM in > vma_assert_[write_]locked(), but this doesn't seem to be a problem. > > In addition, there were already inconsistencies - vma_assert_write_locked() > uses VM_WARN_ON_ONCE_VMA() and performs no actions if CONFIG_DEBUG_VM is > not set, and vma_assert_locked() looked up vma->vm_refcnt but also only > asserted if CONFIG_DEBUG_VM was set. > > Therefore simply update these functions such that they're predicated on > CONFIG_DEBUG_VM and update their kdoc descriptions accordingly. > > Signed-off-by: Lorenzo Stoakes (ARM) Reviewed-by: Vlastimil Babka (SUSE) > --- > include/linux/mmap_lock.h | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h > index 9367430ee53c..bada7a03ddf4 100644 > --- a/include/linux/mmap_lock.h > +++ b/include/linux/mmap_lock.h > @@ -354,9 +354,14 @@ int vma_start_write_killable(struct vm_area_struct *vma) > /** > * vma_assert_write_locked() - assert that @vma holds a VMA write lock. > * @vma: The VMA to assert. > + * > + * Assert only if CONFIG_DEBUG_VM is set. > */ > static inline void vma_assert_write_locked(const struct vm_area_struct *vma) > { > + if (!IS_ENABLED(CONFIG_DEBUG_VM)) > + return; > + > if (!IS_ENABLED(CONFIG_MMU)) { > mmap_assert_write_locked(vma->vm_mm); > return; > @@ -369,11 +374,16 @@ static inline void vma_assert_write_locked(const struct vm_area_struct *vma) > * vma_assert_locked() - assert that @vma holds either a VMA read or a VMA write > * lock and is not detached. > * @vma: The VMA to assert. > + * > + * Assert only if CONFIG_DEBUG_VM is set. > */ > static inline void vma_assert_locked(const struct vm_area_struct *vma) > { > unsigned int refcnt; > > + if (!IS_ENABLED(CONFIG_DEBUG_VM)) > + return; > + > if (!IS_ENABLED(CONFIG_MMU)) { > mmap_assert_locked(vma->vm_mm); > return; > @@ -480,12 +490,12 @@ static inline void vma_assert_attached(struct vm_area_struct *vma) > if (!IS_ENABLED(CONFIG_MMU)) > return; > > - WARN_ON_ONCE(!vma_is_attached(vma)); > + VM_WARN_ON_ONCE(!vma_is_attached(vma)); > } > > static inline void vma_assert_detached(struct vm_area_struct *vma) > { > - WARN_ON_ONCE(vma_is_attached(vma)); > + VM_WARN_ON_ONCE(vma_is_attached(vma)); > } > > static inline void vma_mark_attached(struct vm_area_struct *vma) > @@ -549,6 +559,9 @@ struct vm_area_struct *lock_next_vma(struct vma_rcu_iter *rvmi, > > static inline void vma_assert_can_modify(struct vm_area_struct *vma) > { > + if (!IS_ENABLED(CONFIG_DEBUG_VM)) > + return; > + > if (vma_is_attached(vma)) > vma_assert_write_locked(vma); > } >