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Mon, 25 May 2026 04:06:45 -0700 (PDT) Message-ID: Date: Mon, 25 May 2026 19:06:40 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US From: Yadan Fan Subject: MIPS: mm: Fix out-of-bounds write in maar_res_walk() To: tsbogend@alpha.franken.de Cc: akpm@linux-foundation.org, rppt@kernel.org, liam@infradead.org, catalin.marinas@arm.com, jiaxun.yang@flygoat.com, paulburton@kernel.org, linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, ydfan@suse.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" maar_res_walk() uses wi->num_cfg as the index into the fixed-size wi->cfg array, but checks whether the array is full only after it has filled the selected entry. If walk_system_ram_range() reports more than 16 memory ranges, the overflow call writes one struct maar_config past the end of the array before WARN_ON() prevents num_cfg from advancing. Move the full-array check before taking the array slot. Keep the existing behavior of warning and returning 0 when the scratch array has no room left. Fixes: a5718fe8f70f ("MIPS: mm: Drop boot_mem_map") Signed-off-by: Yadan Fan --- arch/mips/mm/init.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c index 55b25e85122a..0ba958b7ffa5 100644 --- a/arch/mips/mm/init.c +++ b/arch/mips/mm/init.c @@ -272,9 +272,15 @@ static int maar_res_walk(unsigned long start_pfn, unsi= gned long nr_pages, void *data) { struct maar_walk_info *wi =3D data; - struct maar_config *cfg =3D &wi->cfg[wi->num_cfg]; + struct maar_config *cfg; unsigned int maar_align; =20 + /* Ensure we don't overflow the cfg array */ + if (WARN_ON(wi->num_cfg >=3D ARRAY_SIZE(wi->cfg))) + return 0; + + cfg =3D &wi->cfg[wi->num_cfg]; + /* MAAR registers hold physical addresses right shifted by 4 bits */ maar_align =3D BIT(MIPS_MAAR_ADDR_SHIFT + 4); =20 @@ -283,9 +289,7 @@ static int maar_res_walk(unsigned long start_pfn, unsig= ned long nr_pages, cfg->upper =3D ALIGN_DOWN(PFN_PHYS(start_pfn + nr_pages), maar_align) - 1; cfg->attrs =3D MIPS_MAAR_S; =20 - /* Ensure we don't overflow the cfg array */ - if (!WARN_ON(wi->num_cfg >=3D ARRAY_SIZE(wi->cfg))) - wi->num_cfg++; + wi->num_cfg++; =20 return 0; } --=20 2.51.0