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b=DDurZJ/tH9/Dcq2NUUAnR7bwtgDl5thIrctfw+s4q4F7B9z+LCEL9V4leztRfz6Oy QN+ti9o7Lk4il2Xp2hnzjsN60DUZJkyYwxwhGWgCcp/J6tv9XrZpdoii3QHMM6q8IS FBIF1WP+glbZTrUhUIkqwPEPvI4kpzhkxsSOShA4= Date: Wed, 18 Oct 2023 08:52:48 -0700 From: Andrew Morton To: Baoquan He Cc: Dan Carpenter , Philip Li , oe-kbuild@lists.linux.dev, Lorenzo Stoakes , lkp@intel.com, oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org, Linux Memory Management List Subject: Re: mm/vmalloc.c:3689 vread_iter() error: we previously assumed 'vm' could be null (see line 3667) Message-Id: <20231018085248.6f3f36101cbdfe0990c8b467@linux-foundation.org> In-Reply-To: References: <89caf59a-d3b9-409d-b1ae-9e370cb9ee7d@kadam.mountain> 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-Queue-Id: BE93040025 X-Rspam-User: X-Stat-Signature: c6o4m5br6wscmdab4ydeuzhgwf83bkit X-Rspamd-Server: rspam01 X-HE-Tag: 1697644372-462877 X-HE-Meta: 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 vRtCYjAz gxn8+30ddx0lru8YmksllH1fsXwNtfsdbvXgrHQtqUee1S+tGXlvJYluMCsC4bUYsNLg7tSU37VrmPrgv3keMQnUKZKNJxzQZAHEvdPcpruKh2UzV/El7I1+u2N8sm6lIJ8e6n4iwYf04niFaGY2KzJMz05TrjgzFBlEZ5PalUJPJP4uP8icZcx6JlBDTpaoLC0TsyvhYKZa2oWaFjndt5MFnvS69qFf4F4Xd8kmVEZHjgvzs5HHfPvDdA0M6M55j3x9sh3VCyMkcQtBOt66xPnK59yEK9+r8k8FU9rXscHkSFo0= 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 Wed, 18 Oct 2023 23:15:31 +0800 Baoquan He wrote: > From: Baoquan He > Date: Wed, 18 Oct 2023 22:50:14 +0800 > Subject: [PATCH] mm/vmalloc: fix the unchecked dereference warning in vread_iter() > Content-type: text/plain > > LKP reported smatch warning as below: > > =================== > smatch warnings: > mm/vmalloc.c:3689 vread_iter() error: we previously assumed 'vm' could be null (see line 3667) > ...... > 06c8994626d1b7 @3667 size = vm ? get_vm_area_size(vm) : va_size(va); > ...... > 06c8994626d1b7 @3689 else if (!(vm->flags & VM_IOREMAP)) > ^^^^^^^^^ > Unchecked dereference > ===================== > > So add checking on whether 'vm' is not null when dereferencing it in > vread_iter(). This mutes smatch complaint. > > ... > > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3813,7 +3813,7 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count) > > if (flags & VMAP_RAM) > copied = vmap_ram_vread_iter(iter, addr, n, flags); > - else if (!(vm->flags & VM_IOREMAP)) > + else if (!(vm && (vm->flags & VM_IOREMAP))) > copied = aligned_vread_iter(iter, addr, n); > else /* IOREMAP area is treated as memory hole */ > copied = zero_iter(iter, n); So is this not a real runtime bug? We're only doing this to suppress a smatch warning? If so, can we please include a description of *why* this wasn't a bug? What conditions ensure that vm!=NULL at this point?