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h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Th5tIDewprZendX4fGigw2vL+8B1sr/APy/gtFAfVfQbS6Lk2IhTZpZA5WLxIvgtJ j/L5UqaKKe48k3fkMYGmV6bII35mRZZbn6CwZnuzuiCAzemSUUXvNoELHQ2ONuX4iL UTro6N5WVRrvVYbuoHwHPeoK3huWHGz9+LEO25VRTXpW3BkKMf5L0mJDWuZFvZCaLp rQIs2ITzWhuEBZJtF9A+ErJoBM+350SBMkJ6vpoNJHIa18H8plUq/3CaNZWmHMywZd VKrluIioL8pbB880mGbp917rCZDAWn59BtwIBa7rEcyQJRC3/MQeiSi2IX/BKMHJSb gTOT1W1JropBQ== Date: Sun, 8 Nov 2026 13:05:11 +0200 From: Mike Rapoport To: Radhey Shyam Pandey Cc: robh@kernel.org, saravanak@kernel.org, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, m.szyprowski@samsung.com, robin.murphy@arm.com, baoquan.he@linux.dev, pasha.tatashin@soleen.com, pratyush@kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux.dev, kexec@lists.infradead.org Subject: Re: [PATCH 3/4] mm/cma: reject CMA areas that overlap the kernel image Message-ID: References: <20261103162429.2053989-1-radhey.shyam.pandey@amd.com> <20261103162429.2053989-4-radhey.shyam.pandey@amd.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261103162429.2053989-4-radhey.shyam.pandey@amd.com> X-Stat-Signature: ugea76cuegjwnffu1jee9mb9a55mnhxj X-Rspamd-Queue-Id: 41706140006 X-Rspam-User: X-Rspamd-Server: rspam11 X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1794135923-260342 X-HE-Meta: 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 vxpioigm E4ycQTVL8HYnDHuW2bcV5F3R1DMS9kTOsPMvNPmocztK+rTsIVRBZfWe/lFUtJrq7mwnHE0qdr41OOfo6AAxKLo8jk3EHY3JjrHY1GsmWp+tUubKvgVzmeu9alAzEWbZxfOr8fr0TA4TKilsNtqhffL2RYz6g7/q+GRrHrVBuU9bIyvGpSIl+t3QWVrtHH2BpnfmB+UkHmt59MmF1lfoubN/b8j/ZBs9itsZS/gbApbUibhPhVG9VfgwU+VoK1H4yCuOFkGuairzLmSzeOM7mnDm2gA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hi, On Tue, Nov 03, 2026 at 09:54:28PM +0530, Radhey Shyam Pandey wrote: > cma_init_reserved_mem() takes a base chosen by its caller and only requires > that the range already be reserved, so an overlap with the kernel image is > indistinguishable from the normal case. cma_activate_area() then clears > PageReserved on those pages and frees them into MIGRATE_CMA, overriding the > memblock_reserve() of [_text, _end), so live kernel text reaches userspace. > kexec reached this until the fix this series builds on; a device tree > placing a shared-dma-pool over where the bootloader loaded the kernel still > can. Reject the overlap rather than let such a caller corrupt the kernel. > > Signed-off-by: Radhey Shyam Pandey > --- > Changes since RFC: > - Drop Pratyush reviewed-by tag as there were few changes. > - Trim the commit description. > - Drop the redundant comment as suggested by Mike. > - cma_overlaps_kernel_image() is kept as helpers in asm-generic/sections.h > are virtual-address helpers. > --- > mm/cma.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/mm/cma.c b/mm/cma.c > index 9c53b2b70dc8..3231a53161cd 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -31,6 +31,8 @@ > #include > #include > > +#include You probably don't need this. > + > #include "internal.h" > #include "cma.h" > #include "mm_init.h" > @@ -68,6 +70,16 @@ bool cma_has_dynamic_base(const struct cma *cma) > return test_bit(CMA_DYNAMIC_BASE, &cma->flags); > } > > +static bool cma_overlaps_kernel_image(phys_addr_t base, phys_addr_t size) > +{ > + phys_addr_t end; > + > + if (check_add_overflow(base, size, &end)) > + return true; > + > + return base < __pa_symbol(_end) && __pa_symbol(_text) < end; > +} > + > static unsigned long cma_bitmap_aligned_mask(const struct cma *cma, > unsigned int align_order) > { > @@ -295,6 +307,15 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size, > if (!size || !memblock_is_region_reserved(base, size)) > return -EINVAL; > > + if (cma_overlaps_kernel_image(base, size)) { > + phys_addr_t text = __pa_symbol(_text); > + phys_addr_t end = __pa_symbol(_end); > + > + pr_err("area %s (%pa, size %pa) overlaps kernel image [%pa-%pa]\n", > + name ?: "(unnamed)", &base, &size, &text, &end); We don't want to expose addresses of the kernel image. I'd drop text, end, and probably even base from the printout. > + return -EBUSY; > + } > + > /* > * CMA uses CMA_MIN_ALIGNMENT_BYTES as alignment requirement which > * needs pageblock_order to be initialized. Let's enforce it. > -- > 2.44.4 > -- Sincerely yours, Mike.