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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7ae75637909sm255127285a.68.2024.10.07.06.25.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Oct 2024 06:25:02 -0700 (PDT) Date: Mon, 7 Oct 2024 09:25:00 -0400 From: Peter Xu To: manas18244@iiitd.ac.in Cc: Andrew Morton , Shuah Khan , Anup Sharma , linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+093d096417e7038a689b@syzkaller.appspotmail.com Subject: Re: [PATCH v4] Fixes: null pointer dereference in pfnmap_lockdep_assert Message-ID: References: <20241004-fix-null-deref-v4-1-d0a8ec01ac85@iiitd.ac.in> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241004-fix-null-deref-v4-1-d0a8ec01ac85@iiitd.ac.in> On Fri, Oct 04, 2024 at 11:12:16PM +0530, Manas via B4 Relay wrote: > From: Manas > > syzbot has pointed to a possible null pointer dereference in > pfnmap_lockdep_assert. vm_file member of vm_area_struct is being > dereferenced without any checks. > > This fix assigns mapping only if vm_file is not NULL. > > Reported-by: syzbot+093d096417e7038a689b@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b > --- > This bug[1] triggers a general protection fault in follow_pfnmap_start > function. An assertion pfnmap_lockdep_assert inside this function > dereferences vm_file member of vm_area_struct. And panic gets triggered > when vm_file is NULL. > > This patch assigns mapping only if vm_file is not NULL. > > [1] https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b > > Signed-off-by: Manas Reviewed-by: Peter Xu -- Peter Xu