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Howlett" , Jann Horn , stable@vger.kernel.org Subject: Re: [PATCH hotfix 6.12 v2] mm/mlock: set the correct prev on failure Message-ID: <20241028024753.yqteimzthoj2rmmi@master> Reply-To: Wei Yang References: <20241027123321.19511-1-richard.weiyang@gmail.com> <20241027175347.af0faeac9fdfc2fc8ae051e9@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241027175347.af0faeac9fdfc2fc8ae051e9@linux-foundation.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspam-User: X-Stat-Signature: q3m4jmmrmfgd71r45h946y6m8yac8f4z X-Rspamd-Queue-Id: B0198C000F X-Rspamd-Server: rspam11 X-HE-Tag: 1730083650-196592 X-HE-Meta: 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 w0PLfWxZ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000990, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Oct 27, 2024 at 05:53:47PM -0700, Andrew Morton wrote: >On Sun, 27 Oct 2024 12:33:21 +0000 Wei Yang wrote: > >> After commit 94d7d9233951 ("mm: abstract the vma_merge()/split_vma() >> pattern for mprotect() et al."), if vma_modify_flags() return error, the >> vma is set to an error code. This will lead to an invalid prev be >> returned. >> >> Generally this shouldn't matter as the caller should treat an error as >> indicating state is now invalidated, however unfortunately >> apply_mlockall_flags() does not check for errors and assumes that >> mlock_fixup() correctly maintains prev even if an error were to occur. > >And what is the userspace-visible effect when this occurs? > When error occurs, prev would be set to (-ENOMEM). And accessing this address would lead to a kernel crash. So looks no userspace-visible effect for this. -- Wei Yang Help you, Help me