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[218.102.100.68]) by smtp.gmail.com with ESMTPSA id c5-20020a170902c2c500b0016beea47800sm152394pla.41.2022.07.08.17.55.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Jul 2022 17:55:28 -0700 (PDT) From: Hawkins Jiawei To: chenxiaosong2@huawei.com Cc: akpm@linux-foundation.org, anton@tuxera.com, linux-kernel@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, liuyongqiang13@huawei.com, yi.zhang@huawei.com, zhangxiaoxu5@huawei.com, 18801353760@163.com, skhan@linuxfoundation.org, paskripkin@gmail.com, linux-kernel-mentees@lists.linuxfoundation.org Subject: Re: [PATCH v2] ntfs: fix use-after-free in ntfs_ucsncmp() Date: Sat, 9 Jul 2022 08:54:51 +0800 Message-Id: <20220709005450.2220-1-yin31149@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220707105329.4020708-1-chenxiaosong2@huawei.com> References: <20220707105329.4020708-1-chenxiaosong2@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Fix this by adding sanity check on end address of attibute name string. > diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c > index 4de597a83b88..9ab8766872d2 100644 > --- a/fs/ntfs/attrib.c > +++ b/fs/ntfs/attrib.c > @@ -592,8 +592,12 @@ static int ntfs_attr_find(const ATTR_TYPE type, const ntfschar *name, > a = (ATTR_RECORD*)((u8*)ctx->attr + > le32_to_cpu(ctx->attr->length)); > for (;; a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length))) { > - if ((u8*)a < (u8*)ctx->mrec || (u8*)a > (u8*)ctx->mrec + > - le32_to_cpu(ctx->mrec->bytes_allocated)) > + u8 *mrec_end = (u8 *)ctx->mrec + > + le32_to_cpu(ctx->mrec->bytes_allocated); > + u8 *name_end = (u8 *)a + le16_to_cpu(a->name_offset) + > + a->name_length; In my opinion, name_length field just means the number of characters, yet each character is a ntfschar type. So name should be name_length * sizeof(ntfschar) bytes. The example is at https://elixir.bootlin.com/linux/v5.19-rc5/source/fs/ntfs/attrib.c#L1667 > + if ((u8*)a < (u8*)ctx->mrec || (u8*)a > mrec_end || > + name_end > mrec_end) > break; > ctx->attr = a; > if (unlikely(le32_to_cpu(a->type) > le32_to_cpu(type) || > --