{"id":"CVE-2021-47638","state":"PUBLISHED","title":"ubifs: rename_whiteout: Fix double free for whiteout_ui->data","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nubifs: rename_whiteout: Fix double free for whiteout_ui->data\n\n'whiteout_ui->data' will be freed twice if space budget fail for\nrename whiteout operation as following process:\n\nrename_whiteout\n  dev = kmalloc\n  whiteout_ui->data = dev\n  kfree(whiteout_ui->data)  // Free first time\n  iput(whiteout)\n    ubifs_free_inode\n      kfree(ui->data)\t    // Double free!\n\nKASAN reports:\n==================================================================\nBUG: KASAN: double-free or invalid-free in ubifs_free_inode+0x4f/0x70\nCall Trace:\n  kfree+0x117/0x490\n  ubifs_free_inode+0x4f/0x70 [ubifs]\n  i_callback+0x30/0x60\n  rcu_do_batch+0x366/0xac0\n  __do_softirq+0x133/0x57f\n\nAllocated by task 1506:\n  kmem_cache_alloc_trace+0x3c2/0x7a0\n  do_rename+0x9b7/0x1150 [ubifs]\n  ubifs_rename+0x106/0x1f0 [ubifs]\n  do_syscall_64+0x35/0x80\n\nFreed by task 1506:\n  kfree+0x117/0x490\n  do_rename.cold+0x53/0x8a [ubifs]\n  ubifs_rename+0x106/0x1f0 [ubifs]\n  do_syscall_64+0x35/0x80\n\nThe buggy address belongs to the object at ffff88810238bed8 which\nbelongs to the cache kmalloc-8 of size 8\n==================================================================\n\nLet ubifs_free_inode() free 'whiteout_ui->data'. BTW, delete unused\nassignment 'whiteout_ui->data_len = 0', process 'ubifs_evict_inode()\n-> ubifs_jnl_delete_inode() -> ubifs_jnl_write_inode()' doesn't need it\n(because 'inc_nlink(whiteout)' won't be excuted by 'goto out_release',\n and the nlink of whiteout inode is 0).","publishedAt":"2025-02-26T01:54:11.178Z","updatedAt":"2026-08-05T08:48:43.826Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"8b3c7be16f3f4dfd6e15ac651484e59d3fa36274","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"2b3236ecf96db7af5836e1366ce39ace8ce832fa","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"14276d38c89a170363e90b6ac0a53c3cf61b87fc","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"a90e2dbe66d2647ff95a0442ad2e86482d977fd8","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"2ad07009c459e56ebdcc089d850d664660fdb742","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"b9a937f096e608b3368c1abc920d4d640ba2c94f","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"6d7a158a7363c1f6604aa47ae1a280a5c65123dd","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"40a8f0d5e7b3999f096570edab71c345da812e3e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ubifs/dir.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.9","versionType":"semver"},{"version":"4.14.276","status":"unaffected","lessThanOrEqual":"4.14.*","versionType":"semver"},{"version":"4.19.238","status":"unaffected","lessThanOrEqual":"4.19.*","versionType":"semver"},{"version":"5.4.189","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.110","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.33","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"5.16.19","status":"unaffected","lessThanOrEqual":"5.16.*","versionType":"semver"},{"version":"5.17.2","status":"unaffected","lessThanOrEqual":"5.17.*","versionType":"semver"},{"version":"5.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ubifs/dir.c"]}],"references":["https://git.kernel.org/stable/c/8b3c7be16f3f4dfd6e15ac651484e59d3fa36274","https://git.kernel.org/stable/c/2b3236ecf96db7af5836e1366ce39ace8ce832fa","https://git.kernel.org/stable/c/14276d38c89a170363e90b6ac0a53c3cf61b87fc","https://git.kernel.org/stable/c/a90e2dbe66d2647ff95a0442ad2e86482d977fd8","https://git.kernel.org/stable/c/2ad07009c459e56ebdcc089d850d664660fdb742","https://git.kernel.org/stable/c/b9a937f096e608b3368c1abc920d4d640ba2c94f","https://git.kernel.org/stable/c/6d7a158a7363c1f6604aa47ae1a280a5c65123dd","https://git.kernel.org/stable/c/40a8f0d5e7b3999f096570edab71c345da812e3e"],"weaknesses":["CWE-415"],"ingestedAt":"2026-10-29T19:49:19.404Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/47xxx/CVE-2021-47638.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-47638","state":"PUBLISHED","datePublished":"2025-02-26T01:54:11.178Z","dateUpdated":"2026-08-05T08:48:43.826Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-02-26T01:48:21.519Z"},"containers":{"cna":{"title":"ubifs: rename_whiteout: Fix double free for whiteout_ui->data","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nubifs: rename_whiteout: Fix double free for whiteout_ui->data\n\n'whiteout_ui->data' will be freed twice if space budget fail for\nrename whiteout operation as following process:\n\nrename_whiteout\n  dev = kmalloc\n  whiteout_ui->data = dev\n  kfree(whiteout_ui->data)  // Free first time\n  iput(whiteout)\n    ubifs_free_inode\n      kfree(ui->data)\t    // Double free!\n\nKASAN reports:\n==================================================================\nBUG: KASAN: double-free or invalid-free in ubifs_free_inode+0x4f/0x70\nCall Trace:\n  kfree+0x117/0x490\n  ubifs_free_inode+0x4f/0x70 [ubifs]\n  i_callback+0x30/0x60\n  rcu_do_batch+0x366/0xac0\n  __do_softirq+0x133/0x57f\n\nAllocated by task 1506:\n  kmem_cache_alloc_trace+0x3c2/0x7a0\n  do_rename+0x9b7/0x1150 [ubifs]\n  ubifs_rename+0x106/0x1f0 [ubifs]\n  do_syscall_64+0x35/0x80\n\nFreed by task 1506:\n  kfree+0x117/0x490\n  do_rename.cold+0x53/0x8a [ubifs]\n  ubifs_rename+0x106/0x1f0 [ubifs]\n  do_syscall_64+0x35/0x80\n\nThe buggy address belongs to the object at ffff88810238bed8 which\nbelongs to the cache kmalloc-8 of size 8\n==================================================================\n\nLet ubifs_free_inode() free 'whiteout_ui->data'. BTW, delete unused\nassignment 'whiteout_ui->data_len = 0', process 'ubifs_evict_inode()\n-> ubifs_jnl_delete_inode() -> ubifs_jnl_write_inode()' doesn't need it\n(because 'inc_nlink(whiteout)' won't be excuted by 'goto out_release',\n and the nlink of whiteout inode is 0)."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"8b3c7be16f3f4dfd6e15ac651484e59d3fa36274","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"2b3236ecf96db7af5836e1366ce39ace8ce832fa","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"14276d38c89a170363e90b6ac0a53c3cf61b87fc","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"a90e2dbe66d2647ff95a0442ad2e86482d977fd8","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"2ad07009c459e56ebdcc089d850d664660fdb742","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"b9a937f096e608b3368c1abc920d4d640ba2c94f","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"6d7a158a7363c1f6604aa47ae1a280a5c65123dd","versionType":"git"},{"version":"9e0a1fff8db56eaaebb74b4a3ef65f86811c4798","status":"affected","lessThan":"40a8f0d5e7b3999f096570edab71c345da812e3e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ubifs/dir.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.9","versionType":"semver"},{"version":"4.14.276","status":"unaffected","lessThanOrEqual":"4.14.*","versionType":"semver"},{"version":"4.19.238","status":"unaffected","lessThanOrEqual":"4.19.*","versionType":"semver"},{"version":"5.4.189","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.110","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.33","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"5.16.19","status":"unaffected","lessThanOrEqual":"5.16.*","versionType":"semver"},{"version":"5.17.2","status":"unaffected","lessThanOrEqual":"5.17.*","versionType":"semver"},{"version":"5.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ubifs/dir.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/8b3c7be16f3f4dfd6e15ac651484e59d3fa36274"},{"url":"https://git.kernel.org/stable/c/2b3236ecf96db7af5836e1366ce39ace8ce832fa"},{"url":"https://git.kernel.org/stable/c/14276d38c89a170363e90b6ac0a53c3cf61b87fc"},{"url":"https://git.kernel.org/stable/c/a90e2dbe66d2647ff95a0442ad2e86482d977fd8"},{"url":"https://git.kernel.org/stable/c/2ad07009c459e56ebdcc089d850d664660fdb742"},{"url":"https://git.kernel.org/stable/c/b9a937f096e608b3368c1abc920d4d640ba2c94f"},{"url":"https://git.kernel.org/stable/c/6d7a158a7363c1f6604aa47ae1a280a5c65123dd"},{"url":"https://git.kernel.org/stable/c/40a8f0d5e7b3999f096570edab71c345da812e3e"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached via renameat2(RENAME_WHITEOUT) on a mounted UBIFS volume (syscall → vfs_rename → ubifs_rename → do_rename), not via network packet processing.\nAC:L - An attacker with write access can reliably force the whiteout ubifs_budget_space() failure by exhausting free space or concurrent budget pressure after earlier budgets succeed; no conditions outside attacker control are required.\nPR:L - RENAME_WHITEOUT needs only directory write/exec permission; CAP_MKNOD is not required (unprivileged whiteouts since a3c751a50fe6), so a normal local user on writable UBIFS (e.g. Android/embedded data) can trigger it.\nUI:N - The attacker issues renameat2 themselves on an already-mounted writable UBIFS; no separate victim action is required.\nS:U - Impact is confined to the local kernel/host authority (privilege escalation or crash); it does not cross a VM, IOMMU, or other security boundary.\nC:H - This is a double-free of a kmalloc object with an RCU grace period before the second free, enabling heap reclaim and arbitrary read primitives from corrupted allocator/object state.\nI:H - The same double-free/heap corruption is exploitable for arbitrary write and control-flow hijacking via spraying the reclaimed kmalloc-8 slot between the two frees.\nA:H - The double-free triggers KASAN/invalid-free and can oops or panic the kernel even without full exploitation."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T08:48:43.826Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"4.14.276"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"4.19.238"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.4.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.10.110"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.15.33"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.16.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.17.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.18"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":5.5,"attackVector":"LOCAL","baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","integrityImpact":"NONE","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"NONE"}},{"other":{"type":"ssvc","content":{"id":"CVE-2021-47638","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2025-10-01T19:50:47.905064Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-415","lang":"en","type":"CWE","description":"CWE-415 Double Free"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-10-01T19:57:08.545Z"}}]}}}