{"api_version":"1","generated_at":"2026-09-11T22:32:23+00:00","cve":"CVE-2026-89704","urls":{"html":"https://cve.report/CVE-2026-89704","api":"https://cve.report/api/cve/CVE-2026-89704.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89704","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89704"},"summary":{"title":"nfsd: sample writeback error cursor before async COPY loop","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: sample writeback error cursor before async COPY loop\n\n_nfsd_copy_file_range() samples dst->f_wb_err into \"since\"\nafter the copy loop, then uses it to detect writeback errors\nvia filemap_check_wb_err() once vfs_fsync_range() returns.\nBecause the nfsd_file cache reuses a single struct file\nacross requests targeting the same inode, a concurrent\nCOMMIT or stable WRITE on dst advances dst->f_wb_err to the\ncurrent mapping->wb_err via file_check_and_advance_wb_err()\nduring its own vfs_fsync_range(). If that advancement lands\nbetween the writeback error appearing in mapping->wb_err\nand the COPY worker sampling \"since\", the worker captures\nthe already-advanced cursor, errseq_check() sees cur ==\nsince and returns zero, and NFSD4_COPY_F_COMMITTED is set\neven though writeback failed. CB_OFFLOAD then encodes\nwr_stable_how = FILE_SYNC4, the client treats the copied\ndata as durable, and the failure becomes silent data loss.\n\nSample since once at the start of the function. The cursor\nthen reflects state in effect before this COPY issues any\nwrites, and filemap_check_wb_err() detects any error that\noccurs during the copy regardless of which thread first\nobserves it. This matches the pattern used by\nnfsd_vfs_write() and nfsd4_clone_file_range().","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:57","updated_at":"2026-09-11 20:19:57"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363","name":"https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2","name":"https://git.kernel.org/stable/c/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169","name":"https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046","name":"https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89704","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89704","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb 52b2db7a72e19ac2686fa4b2a52406661e7bf9e2 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb 8277d4a11ae2cb5495842be558fd946032c24363 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb a1cbafe756cd5e6ab0e099062f37da7a5b081169 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb 20a67a7d18221af736f124770c2c5e859b479046 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f14816f2f928c560d28ba344af689f56efcd6f55 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3145fe0ebb16e1715ad541a301bc6675c8375fcd git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.10.124 5.11 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.15.49 5.16 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.17","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.17 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.109 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.50 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/nfsd/nfs4proc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"52b2db7a72e19ac2686fa4b2a52406661e7bf9e2","status":"affected","version":"555dbf1a9aac6d3150c8b52fa35f768a692f4eeb","versionType":"git"},{"lessThan":"8277d4a11ae2cb5495842be558fd946032c24363","status":"affected","version":"555dbf1a9aac6d3150c8b52fa35f768a692f4eeb","versionType":"git"},{"lessThan":"a1cbafe756cd5e6ab0e099062f37da7a5b081169","status":"affected","version":"555dbf1a9aac6d3150c8b52fa35f768a692f4eeb","versionType":"git"},{"lessThan":"20a67a7d18221af736f124770c2c5e859b479046","status":"affected","version":"555dbf1a9aac6d3150c8b52fa35f768a692f4eeb","versionType":"git"},{"status":"affected","version":"f14816f2f928c560d28ba344af689f56efcd6f55","versionType":"git"},{"status":"affected","version":"3145fe0ebb16e1715ad541a301bc6675c8375fcd","versionType":"git"},{"lessThan":"5.11","status":"affected","version":"5.10.124","versionType":"semver"},{"lessThan":"5.16","status":"affected","version":"5.15.49","versionType":"semver"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/nfsd/nfs4proc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.17"},{"lessThan":"5.17","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.109","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.50","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.109","versionStartIncluding":"5.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.50","versionStartIncluding":"5.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"5.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"5.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.124","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.49","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: sample writeback error cursor before async COPY loop\n\n_nfsd_copy_file_range() samples dst->f_wb_err into \"since\"\nafter the copy loop, then uses it to detect writeback errors\nvia filemap_check_wb_err() once vfs_fsync_range() returns.\nBecause the nfsd_file cache reuses a single struct file\nacross requests targeting the same inode, a concurrent\nCOMMIT or stable WRITE on dst advances dst->f_wb_err to the\ncurrent mapping->wb_err via file_check_and_advance_wb_err()\nduring its own vfs_fsync_range(). If that advancement lands\nbetween the writeback error appearing in mapping->wb_err\nand the COPY worker sampling \"since\", the worker captures\nthe already-advanced cursor, errseq_check() sees cur ==\nsince and returns zero, and NFSD4_COPY_F_COMMITTED is set\neven though writeback failed. CB_OFFLOAD then encodes\nwr_stable_how = FILE_SYNC4, the client treats the copied\ndata as durable, and the failure becomes silent data loss.\n\nSample since once at the start of the function. The cursor\nthen reflects state in effect before this COPY issues any\nwrites, and filemap_check_wb_err() detects any error that\noccurs during the copy regardless of which thread first\nobserves it. This matches the pattern used by\nnfsd_vfs_write() and nfsd4_clone_file_range()."}],"providerMetadata":{"dateUpdated":"2026-09-11T19:46:21.039Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2"},{"url":"https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363"},{"url":"https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169"},{"url":"https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046"}],"title":"nfsd: sample writeback error cursor before async COPY loop","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89704","datePublished":"2026-09-11T19:46:21.039Z","dateReserved":"2026-09-11T19:38:34.750Z","dateUpdated":"2026-09-11T19:46:21.039Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:57","lastModifiedDate":"2026-09-11 20:19:57","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89704","Ordinal":"1","Title":"nfsd: sample writeback error cursor before async COPY loop","CVE":"CVE-2026-89704","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89704","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: sample writeback error cursor before async COPY loop\n\n_nfsd_copy_file_range() samples dst->f_wb_err into \"since\"\nafter the copy loop, then uses it to detect writeback errors\nvia filemap_check_wb_err() once vfs_fsync_range() returns.\nBecause the nfsd_file cache reuses a single struct file\nacross requests targeting the same inode, a concurrent\nCOMMIT or stable WRITE on dst advances dst->f_wb_err to the\ncurrent mapping->wb_err via file_check_and_advance_wb_err()\nduring its own vfs_fsync_range(). If that advancement lands\nbetween the writeback error appearing in mapping->wb_err\nand the COPY worker sampling \"since\", the worker captures\nthe already-advanced cursor, errseq_check() sees cur ==\nsince and returns zero, and NFSD4_COPY_F_COMMITTED is set\neven though writeback failed. CB_OFFLOAD then encodes\nwr_stable_how = FILE_SYNC4, the client treats the copied\ndata as durable, and the failure becomes silent data loss.\n\nSample since once at the start of the function. The cursor\nthen reflects state in effect before this COPY issues any\nwrites, and filemap_check_wb_err() detects any error that\noccurs during the copy regardless of which thread first\nobserves it. This matches the pattern used by\nnfsd_vfs_write() and nfsd4_clone_file_range().","Type":"Description","Title":"nfsd: sample writeback error cursor before async COPY loop"}]}}}