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Wed, 20 Mar 2024 15:32:53 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id QlPhK6UB+2W2VQAAD6G6ig (envelope-from ); Wed, 20 Mar 2024 15:32:53 +0000 Date: Wed, 20 Mar 2024 16:32:53 +0100 From: Michal Hocko To: Lee Jones Cc: cve@kernel.org, linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Felix Kuehling Subject: Re: CVE-2024-26628: drm/amdkfd: Fix lock dependency warning Message-ID: References: <2024030649-CVE-2024-26628-f6ce@gregkh> <20240314110938.GM1522089@google.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20240314110938.GM1522089@google.com> X-Spam-Level: Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.com header.s=susede1 header.b=jIIRKzYB X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-2.57 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_DKIM_ALLOW(-0.20)[suse.com:s=susede1]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCPT_COUNT_FIVE(0.00)[5]; NEURAL_HAM_SHORT(-0.20)[-1.000]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.com:s=susede1]; DKIM_TRACE(0.00)[suse.com:+]; MX_GOOD(-0.01)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:dkim]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_NOT_FQDN(0.50)[]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-1.56)[92.15%] X-Spam-Score: -2.57 X-Rspamd-Queue-Id: D8B075BE3C X-Spam-Flag: NO On Thu 14-03-24 11:09:38, Lee Jones wrote: > On Fri, 08 Mar 2024, Michal Hocko wrote: > > > On Wed 06-03-24 06:46:11, Greg KH wrote: > > [...] > > > Possible unsafe locking scenario: > > > > > > CPU0 CPU1 > > > ---- ---- > > > lock(&svms->lock); > > > lock(&mm->mmap_lock); > > > lock(&svms->lock); > > > lock((work_completion)(&svm_bo->eviction_work)); > > > > > > I believe this cannot really lead to a deadlock in practice, because > > > svm_range_evict_svm_bo_worker only takes the mmap_read_lock if the BO > > > refcount is non-0. That means it's impossible that svm_range_bo_release > > > is running concurrently. However, there is no good way to annotate this. > > > > OK, so is this even a bug (not to mention a security/weakness)? > > Looks like the patch fixes a warning which can crash some kernels. So > the CVE appears to be fixing that, rather than the impossible deadlock. Are you talking about lockdep warning or anything else? -- Michal Hocko SUSE Labs