{"id":"CVE-2026-63811","revision":"32473e7b96cf4a61bd1953024c31e2db","records":[{"revision":"32473e7b96cf4a61bd1953024c31e2db","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-63811","aliases":[],"title":"f2fs: read COW data with the original inode during atomic write","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: read COW data with the original inode during atomic write\n\nWhen updating an atomic-write file, f2fs_write_begin() may read the\npreviously written data back from the COW inode:\nprepare_atomic_write_begin() locates the block in the COW inode and sets\nuse_cow, and the read bio is then built with the COW inode:\n\n\tf2fs_submit_page_read(use_cow ? F2FS_I(inode)->cow_inode : inode,\n\t\t\t      ...);\n\nand f2fs_grab_read_bio() decides whether to schedule fs-layer decryption\n(STEP_DECRYPT) for the bio based on that inode via\nfscrypt_inode_uses_fs_layer_crypto().\n\nHowever, the folio being filled belongs to the original inode\n(folio->mapping->host == inode), and the data stored in the COW block was\nencrypted (or left as plaintext) using the original inode's context, not\nthe COW inode's -- see f2fs_encrypt_one_page(), which keys off\nfio->page->mapping->host.  fscrypt_decrypt_pagecache_blocks() likewise\noperates on folio->mapping->host.\n\nThe COW inode is created as a tmpfile in the parent directory and inherits\nits encryption policy from there.  With test_dummy_encryption the newly\ncreated COW inode gets the dummy policy and becomes encrypted, while a\npre-existing regular file -- created before the policy applied, e.g.\nalready present in the on-disk image -- stays unencrypted.  The read\npath then sets STEP_DECRYPT based on the encrypted COW inode and calls\nfscrypt_decrypt_pagecache_blocks() on a folio whose host (the unencrypted\noriginal inode) has a NULL ->i_crypt_info, dereferencing it:\n\n  Oops: general protection fault, probably for non-canonical address ...\n  KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]\n  RIP: 0010:fscrypt_decrypt_pagecache_blocks+0xa0/0x310\n  Workqueue: f2fs_post_read_wq f2fs_post_read_work\n  Call Trace:\n   fscrypt_decrypt_bio+0x1eb/0x340\n   f2fs_post_read_work+0xba/0x140\n   process_one_work+0x91c/0x1a40\n   worker_thread+0x677/0xe90\n   kthread+0x2bc/0x3a0\n\nThe COW inode is only needed to locate the on-disk block, and that block\naddress is already resolved into @blkaddr by prepare_atomic_write_begin()\nvia __find_data_block(cow_inode, ...); f2fs_submit_page_read() then reads\nfrom that physical @blkaddr directly, so the inode argument only selects\nthe post-read crypto context, not which block is fetched.  Reading with\n@inode therefore returns the same (latest, not-yet-committed) COW data,\nwhile making both the fs-layer decryption decision and the inline crypto\npath use the correct (original inode's) key.\n\nWith the COW inode no longer used at the read site, the use_cow flag has no\nremaining consumer; drop it from f2fs_write_begin() and\nprepare_atomic_write_begin().","state":0,"publishedAt":"2026-07-19T12:02:13.057+00:00","modifiedAt":"2026-10-21T12:42:37.074+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/f2fs/data.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"591fc34e1f98b0d7eef4aa3440bfdff3c5a1cadd\",\n                            \"lessThan\": \"bcc9df992f3cbc43f2ecfe0b22e428e50f326e72\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"591fc34e1f98b0d7eef4aa3440bfdff3c5a1cadd\",\n                            \"lessThan\": \"655d55c5740d37ffdf6233ff5fe21cea879407f1\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"591fc34e1f98b0d7eef4aa3440bfdff3c5a1cadd\",\n                            \"lessThan\": \"7e4ab3907f44dc243d026048d7f5d477dae9267b\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"591fc34e1f98b0d7eef4aa3440bfdff3c5a1cadd\",\n                            \"lessThan\": \"a92332f32a8d31a7eee47b1dc1d751cb3319908f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"591fc34e1f98b0d7eef4aa3440bfdff3c5a1cadd\",\n                            \"lessThan\": \"a41075acde0124d2f8a5f563068a5d63e8ffd57b\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/f2fs/data.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.4\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.4\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.160\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.114\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.57\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.1.3\",\n                            \"lessThanOrEqual\": \"7.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/bcc9df992f3cbc43f2ecfe0b22e428e50f326e72","https://git.kernel.org/stable/c/655d55c5740d37ffdf6233ff5fe21cea879407f1","https://git.kernel.org/stable/c/7e4ab3907f44dc243d026048d7f5d477dae9267b","https://git.kernel.org/stable/c/a92332f32a8d31a7eee47b1dc1d751cb3319908f","https://git.kernel.org/stable/c/a41075acde0124d2f8a5f563068a5d63e8ffd57b"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63811","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-63811","identifiers":["CVE-2026-63811"]},"retained":false,"historicalAffected":[]}],"coverage":[]}