From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0F07B1FB51 for ; Tue, 1 Aug 2023 09:29:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83AFCC433C8; Tue, 1 Aug 2023 09:29:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1690882171; bh=VWfNMe8kmAKFD6sqF8IDUl7cmA/NafciYJoUzMKftk0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YufGKSb5Upo9KeX6a656uA0C+MRRNjHdPSum3KeuHSvAHqeOjb4pDem/AKIlZ/FTH eOBmxuphNCdFBW/310Dj044NrMZ7TPoCCIfqtUg3p25tYrgg+j6OIEyRdu+b5eQSfh mzEXtP+vdG082sKftC+In6hfQ096afK/wlDlZGu4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Haren Myneni , Michael Ellerman , Sasha Levin Subject: [PATCH 6.1 011/228] powerpc/pseries/vas: Hold mmap_mutex after mmap lock during window close Date: Tue, 1 Aug 2023 11:17:49 +0200 Message-ID: <20230801091923.243105710@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230801091922.799813980@linuxfoundation.org> References: <20230801091922.799813980@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Haren Myneni [ Upstream commit b59c9dc4d9d47b3c4572d826603fde507055b656 ] Commit 8ef7b9e1765a ("powerpc/pseries/vas: Close windows with DLPAR core removal") unmaps the window paste address and issues HCALL to close window in the hypervisor for migration or DLPAR core removal events. So holds mmap_mutex and then mmap lock before unmap the paste address. But if the user space issue mmap paste address at the same time with the migration event, coproc_mmap() is called after holding the mmap lock which can trigger deadlock when trying to acquire mmap_mutex in coproc_mmap(). t1: mmap() call to mmap t2: Migration event window paste address do_mmap2() migration_store() ksys_mmap_pgoff() pseries_migrate_partition() vm_mmap_pgoff() vas_migration_handler() Acquire mmap lock reconfig_close_windows() do_mmap() lock mmap_mutex mmap_region() Acquire mmap lock call_mmap() //Wait for mmap lock coproc_mmap() unmap vma lock mmap_mutex update window status //wait for mmap_mutex Release mmap lock mmap vma unlock mmap_mutex update window status unlock mmap_mutex ... Release mmap lock Fix this deadlock issue by holding mmap lock first before mmap_mutex in reconfig_close_windows(). Fixes: 8ef7b9e1765a ("powerpc/pseries/vas: Close windows with DLPAR core removal") Signed-off-by: Haren Myneni Signed-off-by: Michael Ellerman Link: https://msgid.link/20230716100506.7833-1-haren@linux.ibm.com Signed-off-by: Sasha Levin --- arch/powerpc/platforms/pseries/vas.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c index 880b962afc057..041a25c08066b 100644 --- a/arch/powerpc/platforms/pseries/vas.c +++ b/arch/powerpc/platforms/pseries/vas.c @@ -744,6 +744,12 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds, } task_ref = &win->vas_win.task_ref; + /* + * VAS mmap (coproc_mmap()) and its fault handler + * (vas_mmap_fault()) are called after holding mmap lock. + * So hold mmap mutex after mmap_lock to avoid deadlock. + */ + mmap_write_lock(task_ref->mm); mutex_lock(&task_ref->mmap_mutex); vma = task_ref->vma; /* @@ -752,7 +758,6 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds, */ win->vas_win.status |= flag; - mmap_write_lock(task_ref->mm); /* * vma is set in the original mapping. But this mapping * is done with mmap() after the window is opened with ioctl. @@ -763,8 +768,8 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds, zap_page_range(vma, vma->vm_start, vma->vm_end - vma->vm_start); - mmap_write_unlock(task_ref->mm); mutex_unlock(&task_ref->mmap_mutex); + mmap_write_unlock(task_ref->mm); /* * Close VAS window in the hypervisor, but do not * free vas_window struct since it may be reused -- 2.39.2