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a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1686980648; bh=BVMmEiv915B72MWDh+k4N5DRLAHb8wLn4DnfeaejgGg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=EQjtHBOfTgfTDp/m2Uzyztq4D5TIdXayeQK9pmNbeTCSDfAw4gYr3nAviXfOhDcbQ lLRRHXUNKxVyx2w2mbYludCh2mmtiPBSyMxgoAOVYnW8AjZJhp1d36jTJYhHEXeHyS 6SnMfoXOswvJPZmseK6puk9Zc7QnVB1efFPICqJM= Date: Fri, 16 Jun 2023 22:44:07 -0700 From: Andrew Morton To: Liam Ni Cc: dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, rppt@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/sparse:avoid null pointer access in memory_present() Message-Id: <20230616224407.863c74a3dc9d4f1427802f91@linux-foundation.org> In-Reply-To: <20230617044036.3985524-1-zhiguangni01@gmail.com> References: <20230617044036.3985524-1-zhiguangni01@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (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-Server: rspam08 X-Rspamd-Queue-Id: 66C5914000A X-Stat-Signature: czf5g1unhburs69dh9friei5esr87zs4 X-Rspam-User: X-HE-Tag: 1686980650-803127 X-HE-Meta: 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 mga/pqVS umK3cc46KUgZdUMXKI6Xd99iC+TYQnC2TMWsfY6ifJZl7Tco9cZXaLZTgztFLoQn6XMDBOJxhKKwjSmL/FpTtu1y2g/fOyv4Cyr9pVCxzXXcgaC8mtKSfllUcc1EcH3UG6wGsyIFeiwlTd2PTH1+J3Z8/qHDj636ay2VP9Vwe9X6u2WYdz8jIcnBrCHMuOOqzdbk/z+wA3YQWbycLKUYGnTIH5h5n5clkvwR2MrjHZSujlkKxCTqYJP0K/gkVc4SnSXx04zLUTP2fRzdZYjwE9OWlOy5vlccysi4VqvSG382ycCyjZyNXw1inMdPjQ5zIqpeSE8Ftw1Ezy4cLbOLCtaEucd/i2yAUaOlExGRXMOlXSpx6eqsRXDECQRZ+xfXNvntaoy7wEWgi2TMxy+rGi6vhCthcrwuyvmNNl182VPmD+cw= 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: On Sat, 17 Jun 2023 14:40:36 +1000 Liam Ni wrote: > __nr_to_section() may return a null pointer, > before accessing the member variable section_mem_map, > we should first determine whether it is a null pointer. > > ... > > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -258,7 +258,7 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en > set_section_nid(section, nid); > > ms = __nr_to_section(section); > - if (!ms->section_mem_map) { > + if (ms && !ms->section_mem_map) { > ms->section_mem_map = sparse_encode_early_nid(nid) | > SECTION_IS_ONLINE; > __section_mark_present(ms, section); I'm suspecting that if __nr_to_section() returns NULL here, we should just panic. But a null-deref gives the same information, so why change things?