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From: Muchun Song In-Reply-To: <55481a8b-dcfc-4bef-ba59-aa0b43dca88b@kernel.org> Date: Wed, 20 May 2026 16:28:32 +0800 Cc: Muchun Song , Andrew Morton , linux-mm@kvack.org, Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Frank van der Linden , Stefan Strogin , Dmitry Safonov <0x7f454c46@gmail.com>, Michal Nazarewicz , linux-kernel@vger.kernel.org, stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20260520061025.3971821-1-songmuchun@bytedance.com> <55481a8b-dcfc-4bef-ba59-aa0b43dca88b@kernel.org> To: "David Hildenbrand (Arm)" X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 8AED7C0009 X-Rspam-User: X-Stat-Signature: c6w3ouzcf1upsw99o9rdpjb4jo5xfjsj X-HE-Tag: 1779265767-602722 X-HE-Meta: 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 3DvyyQep h3BhS5PWo9M13y96ig+MaCyasKCjOYYfk8ObCcNsqjF2cyKWtMnPCt/INeJSzADUzyYf9nIFg2eBNmmySdob7SA5212cG5+XpPfFB8yMtE+EtTzMEJzXMf9mPOukLQFST34A8mYmaBtyHqDC+/QIm/1kBrhDcAWTtS/c8LvYYJVhZF9eD3a7c67SS0rqqhD8EKFsW6F3eSy4k61XHM0qGCno0LFYOc+nBmlZH8UNcaHDewhWHIo8Ws6jDp49laTSP/vFkE0C2WyC7dQBoOuZb47b8dAcoxGSaKtfBS3FXJ5YxonKnlsOq4FZiamHTSdWEYhnc4xWjzHIXPhUwc0AD8a1X7hq57nJpotcTvSeWUKHSBQHts61ZK2eozf1OGanIAkigk4yrsNV0UVYjzmVMsRTWpg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On May 20, 2026, at 16:19, David Hildenbrand (Arm) = wrote: >=20 > On 5/20/26 08:10, Muchun Song wrote: >> cma_activate_area() can fail after allocating range bitmaps. Its = cleanup >> path frees those bitmaps, but only clears cma->count and >> cma->available_count. It leaves cma->nranges and each range's count = in >> place, so cma_debugfs_init() can still register debugfs files for an = area >> that never activated successfully. >>=20 >> That exposes two problems. Reading the bitmap file can make debugfs = walk a >> freed range bitmap and trigger an invalid memory access. Reading = maxchunk >> can also take cma->lock even though that lock is initialized only on = the >> successful activation path. >>=20 >> Fix this by creating debugfs entries only for CMA areas that reached >> CMA_ACTIVATED. >>=20 >> Fixes: c009da4258f9 ("mm, cma: support multiple contiguous ranges, if = requested") >> Fixes: 2e32b947606d ("mm: cma: add functions to get region pages = counters") >> Cc: stable@vger.kernel.org >> Signed-off-by: Muchun Song >> --- >=20 > Acked-by: David Hildenbrand (Arm) Thanks. >=20 > cma_sysfs_init() also traverses all cma_area_count. Does it make sense = to expose > them there? It is better to hide them from users. A separate cleanup patch is better = since there is no critical issue when accessing those sysfs files. Thanks, Muhcun >=20 > --=20 > Cheers, >=20 > David