{"id":"CVE-2026-92500","summary":"ext4: use fsdata to track inline data write state and fix race","details":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: use fsdata to track inline data write state and fix race\n\nInstead of checking the live inode state (ext4_has_inline_data(inode)\nand ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) in the\nwrite_end handlers, use the fsdata parameter of the address space\noperations to explicitly pass down the state in which write_begin\nprepared the write.\n\nA concurrent thread (such as ext4_page_mkwrite()) can convert the\ninline data to an extent between write_begin and write_end. If this\nhappens, the write_end handlers would previously miss the inline\nwrite_end path and fall through to extent-based write_end logic.\nHowever, since block buffers were never allocated in write_begin,\nthis resulted in NULL pointer dereferences or data loss because\nfolio_buffers(folio) was NULL.\n\nDefine EXT4_WRITE_DATA_INLINE (4) as a bit flag (Bit 2), treating\nfsdata as bitwise flags rather than mutually exclusive enums to keep\nstates of the write path independent. Communicate this state via\nfsdata:\n1) ext4_write_begin() and ext4_da_write_begin() set the\n   EXT4_WRITE_DATA_INLINE bit in *fsdata via bitwise OR when an inline\n   write is successfully prepared.\n2) On entry, ext4_write_begin() clears the EXT4_WRITE_DATA_INLINE bit\n   to safely handle VFS retries (where generic_perform_write() bypasses\n   the fsdata initialization on its retry jump).\n3) The write_end handlers perform a bitwise AND to check if the\n   EXT4_WRITE_DATA_INLINE bit is set and invoke the inline write_end\n   helper accordingly.\n\nFurthermore, during a buffered write, ext4_write_inline_data_end()\nacquires the xattr lock after preparing the write. If a concurrent\npage fault (ext4_page_mkwrite()) converts the inline data to an extent\nafter the write_end handlers check the state but before\next4_write_inline_data_end() acquires the xattr write lock, the\nsubsequent check will trigger a kernel panic via\nBUG_ON(!ext4_has_inline_data(inode)).\n\nTo keep git history working and bisectability clean, replace the\nBUG_ON check in ext4_write_inline_data_end() with a graceful error-\nhandling retry path in this same commit. If the inline data is cleared\nafter locking the xattr, we safely release all resources (releasing\niloc.bh, unlocking/putting the folio, stopping the active journal\ntransaction handle) and return 0 (VFS retry) to let the generic write\npath retry the operation safely.","modified":"2026-09-18T03:48:41.437782134Z","published":"2026-09-17T16:10:14.073Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/92xxx/CVE-2026-92500.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/439aedfd7ae868d1d7b4930afe66091cb979cd5c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7edbb323bab2b2a609016014caafdb651c898249"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bd8d74bd46d09905164255b8635fa58b45f41068"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/92xxx/CVE-2026-92500.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-92500"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3fdcfb668fd78ec92d9bc2daddf1d41e2a8a30bb"},{"fixed":"bd8d74bd46d09905164255b8635fa58b45f41068"},{"fixed":"439aedfd7ae868d1d7b4930afe66091cb979cd5c"},{"fixed":"7edbb323bab2b2a609016014caafdb651c898249"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-92500.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.8.0"},{"fixed":"6.18.52"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-92500.json"}}],"schema_version":"1.9.0"}