ext4: validate readdir offset before accessing dirent

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/ext4/dir.c"
                    ],
                    "versions": [
                        {
                            "version": "ac27a0ec112a089f1a5102bc8dffc79c8c815571",
                            "lessThan": "64d445d40e5ea4c4d4d88880db753b370cb69161",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "ac27a0ec112a089f1a5102bc8dffc79c8c815571",
                            "lessThan": "b4c728577933753180e3e97f08424d5bcaff705e",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "ac27a0ec112a089f1a5102bc8dffc79c8c815571",
                            "lessThan": "bc4b7b0414c33b2c8898eb04386df0d21a13dad8",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/ext4/dir.c"
                    ],
                    "versions": [
                        {
                            "version": "2.6.19",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "2.6.19",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.52",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2.6",
                            "lessThanOrEqual": "7.2.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.3",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }