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b=sPPAq2nj0OIdsu/eS2Y8cv3QrxWI6TQ5LTiJeoWbef6L4ZQmJsJy1F0NFLNilExvl iFBm5W1QH0y39aky3kzNNEWCtIvALlFfPbQZttspvt5E927EX1RnJEqgTtdQqPoBML JWe//VpIvf8gGMCJjLc65FDukcJDgUfnRlRzwP8s= Date: Wed, 25 Jun 2025 13:39:09 -0700 From: Andrew Morton To: Christoph Berg Cc: David Hildenbrand , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , "open list:MEMORY MANAGEMENT - MEMORY POLICY AND MIGRATION" , open list Subject: Re: [PATCH] Fix do_pages_stat to use compat_uptr_t Message-Id: <20250625133909.1a054c24d933cd97afd0027d@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 434DB140004 X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: xqphdtdxm3xa9t4omhwyf7h3xptuyfdn X-HE-Tag: 1750883951-217179 X-HE-Meta: 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 7sA290nu SqgCx2YMof9+Ui0TKnRVQTviONwWIHgVFp8jCqm1aMxieIy8wuPMMyK09ZPiX2kEsdXNnlaMdrsz68Sw6EgQ5MoeyB9UJgpW96oseoyM19AJJqhbVafo4/bhNdxwOcGk/FWqtXcgT44NfSylVbQq9YRSZ+HsI0uvwyDGK9MRU2v12BxqC3H1bu6z/xKL6q/+aau4emvCFO5JyEhnWkUWJTiUtX+TJmQ6WBDvVowHQXV8xMV3wcrCx7BU+JzYkit+b1k2n02Mu2B2tQuT9JzL5DVUT3iD8m8KQhodCgeQcPP10VQv3GAKQ6WD9meCs+1LLXaIIVovBaWUjtv8T9ghgd2MVnoupejDdR0fd X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 25 Jun 2025 17:24:14 +0200 Christoph Berg wrote: > For arrays with more than 16 entries, the old code would incorrectly > advance the pages pointer by 16 words instead of 16 compat_uptr_t. > > ... > > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2444,7 +2444,13 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, > if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) > break; > > - pages += chunk_nr; > + if (in_compat_syscall()) { > + compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages; > + > + pages32 += chunk_nr; > + pages = (const void __user * __user *) pages32; > + } else > + pages += chunk_nr; > status += chunk_nr; > nr_pages -= chunk_nr; > } Seems this has been present since 2010. I'll update the Subject: as David suggests and I'll add a cc:stable, thanks. I'll also add a note that David suggested an alternative, so please let's advance that option. Also, a coding-style tweak: --- a/mm/migrate.c~fix-do_pages_stat-to-use-compat_uptr_t-fix +++ a/mm/migrate.c @@ -2449,8 +2449,9 @@ static int do_pages_stat(struct mm_struc pages32 += chunk_nr; pages = (const void __user * __user *) pages32; - } else + } else { pages += chunk_nr; + } status += chunk_nr; nr_pages -= chunk_nr; } _