{"id":"CVE-2026-64029","summary":"ALSA: seq: Serialize UMP output teardown with event_input","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: Serialize UMP output teardown with event_input\n\nseq_ump_process_event() borrows client-\u003eout_rfile.output without\nsynchronizing with the first-open and last-close transition in\nseq_ump_client_open() and seq_ump_client_close().\n\nThe last output unuse can therefore drop opened[STR_OUT] to zero and\nrelease the rawmidi file while an in-flight event_input callback is still\ninside snd_rawmidi_kernel_write(). That leaves the rawmidi substream\nruntime exposed to teardown before the write path has taken its own\nbuffer reference.\n\nAdd a per-client rwlock for the event_input-visible output file. Publish\na newly opened output file under the write side, and hold the read side\nfrom the output lookup through snd_rawmidi_kernel_write(). The last\noutput close copies and clears the visible output file under the write\nside, then drops the lock and releases the saved rawmidi file. Use\nIRQ-safe rwlock guards because event_input can also be reached from\natomic sequencer delivery.\n\nThe buggy scenario involves two paths, with each column showing the\norder within that path:\n\npath A label: event_input path         path B label: last unuse path\n1. seq_ump_process_event() reads       1. seq_ump_client_close()\n   client-\u003eout_rfile.output.              drops opened[STR_OUT] to zero.\n2. snd_rawmidi_kernel_write1()         2. snd_rawmidi_kernel_release()\n   has not yet pinned runtime.            closes the output file.\n3. The writer continues using          3. close_substream() frees\n   the borrowed substream.                substream-\u003eruntime.\n\nThis keeps the output substream and runtime alive for the full\nevent_input write while keeping rawmidi release outside the rwlock.\n\nKASAN reproduced this as a slab-use-after-free in\nsnd_rawmidi_kernel_write1(), with allocation through\nseq_ump_use()/snd_seq_port_connect() and free through\nseq_ump_unuse()/snd_seq_port_disconnect().\n\n\nValidation reproduced this kernel report:\nKASAN slab-use-after-free in snd_rawmidi_kernel_write1+0x9d/0x400\nRIP: 0033:0x7f5528af837f\nRead of size 8\nCall trace:\n  dump_stack_lvl+0x73/0xb0 (?:?)\n  print_report+0xd1/0x650 (?:?)\n  srso_alias_return_thunk+0x5/0xfbef5 (?:?)\n  __virt_addr_valid+0x1a7/0x340 (?:?)\n  kasan_complete_mode_report_info+0x64/0x200 (?:?)\n  kasan_report+0xf7/0x130 (?:?)\n  snd_rawmidi_kernel_write1+0x9d/0x400 (?:?)\n  __asan_load8+0x82/0xb0 (?:?)\n  update_stack_state+0x1ef/0x2d0 (?:?)\n  snd_rawmidi_kernel_write+0x1a/0x20 (?:?)\n  seq_ump_process_event+0xd4/0x120 (sound/core/seq/seq_ump_client.c:82)\n  __snd_seq_deliver_single_event+0x8a/0xe0 (?:?)\n  snd_seq_deliver_from_ump+0x2b2/0xd60 (?:?)\n  lock_acquire+0x14e/0x2e0 (?:?)\n  find_held_lock+0x31/0x90 (?:?)\n  snd_seq_port_use_ptr+0xa6/0xe0 (?:?)\n  __kasan_check_write+0x18/0x20 (?:?)\n  do_raw_read_unlock+0x32/0xa0 (?:?)\n  _raw_read_unlock+0x26/0x50 (?:?)\n  snd_seq_deliver_single_event+0x45c/0x4b0 (?:?)\n  snd_seq_deliver_event+0x10d/0x1b0 (?:?)\n  snd_seq_client_enqueue_event+0x192/0x240 (?:?)\n  snd_seq_write+0x2cd/0x450 (?:?)\n  apparmor_file_permission+0x20/0x30 (?:?)\n  security_file_permission+0x51/0x60 (?:?)\n  vfs_write+0x1ce/0x850 (?:?)\n  __fget_files+0x12b/0x220 (?:?)\n  lock_release+0xc8/0x2a0 (?:?)\n  __rcu_read_unlock+0x74/0x2d0 (?:?)\n  __fget_files+0x135/0x220 (?:?)\n  ksys_write+0x15a/0x180 (?:?)\n  rcu_is_watching+0x24/0x60 (?:?)\n  __x64_sys_write+0x46/0x60 (?:?)\n  x64_sys_call+0x7d/0x20d0 (?:?)\n  do_syscall_64+0xc1/0x360 (arch/x86/entry/syscall_64.c:87)\n  entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)","modified":"2026-07-22T03:32:00.430865552Z","published":"2026-07-19T15:39:20.368Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64029.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0cb1ad795570167558530d6194297ac2396a1991"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/60a1969fae6209644698fca91c185d153674f631"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ef46b616a4c219185bbf10ebcbacb571583fd0e4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64029.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64029"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"81fd444aa371261cd33f31d4ffd80faeeeab0cc9"},{"fixed":"8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb"},{"fixed":"0cb1ad795570167558530d6194297ac2396a1991"},{"fixed":"3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b"},{"fixed":"ef46b616a4c219185bbf10ebcbacb571583fd0e4"},{"fixed":"60a1969fae6209644698fca91c185d153674f631"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64029.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.5.0"},{"fixed":"6.6.142"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.92"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.34"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.11"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64029.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}