Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: midi: Serialize output teardown with event_input event_process_midi() borrows msynth->output_rfile.output and then passes the substream to dump_midi() and snd_rawmidi_kernel_write() without synchronizing with the output open/close transition. midisynth_use() also publishes output_rfile before snd_rawmidi_output_params() has finished. The last midisynth_unuse() can therefore release the same rawmidi file and free substream->runtime before snd_rawmidi_kernel_write1() takes its runtime buffer reference. That leaves the event_input path using a stale substream or runtime and can end in a NULL-deref or use-after-free. Fix this with two pieces of synchronization. Keep a short IRQ-safe spinlock only for publishing or clearing output_rfile and for pairing the output snapshot with an snd_use_lock_t reference. Once event_process_midi() has taken that in-flight reference, it drops the spinlock before calling snd_seq_dump_var_event(), dump_midi(), or snd_rawmidi_kernel_write(). midisynth_unuse() now detaches the visible rawmidi file under the same spinlock, waits for the in-flight writers to drain, and only then drains and releases the saved file. midisynth_use() likewise opens into a local snd_rawmidi_file and publishes it only after snd_rawmidi_output_params() succeeds. The buggy scenario involves two paths, with each column showing the order within that path: event_input path: last unuse path: 1. event_process_midi() snapshots 1. midisynth_unuse() starts output_rfile.output. tearing down output_rfile. 2. dump_midi() reaches 2. snd_rawmidi_kernel_release() snd_rawmidi_kernel_write() closes the output file. before runtime is pinned. 3. close_substream() frees 3. The callback keeps using substream->runtime. the borrowed substream. Validation reproduced this kernel report: KASAN null-ptr-deref in snd_rawmidi_kernel_write1+0x56/0x360 RIP: 0033:0x7fde7dd0837f RIP: 0010:snd_rawmidi_kernel_write1+0x56/0x360
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before f5d470b808bc01f70978e22e595c6f7768313406; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 936641af564c3d92721704b781e36aaf223efdd2; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 718f6a56b40875f19e6915799044a02df9abfd52; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 11165fe2c5ea0516debe486d91df67abbe36905e; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before d6fd2afb137f52bf00c5210cc44d08ed54dcffb4; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before ef7607ab1c8adc6258fb1b27d08e26aecdc18a58 |
| Linux / Linux | affected 2.6.12; unaffected 0 before 2.6.12; unaffected 6.1.178 through 6.1.*; unaffected 6.6.145 through 6.6.*; unaffected 6.12.97 through 6.12.*; unaffected 6.18.40 through 6.18.*; unaffected 7.1.5 through 7.1.*; unaffected 7.2 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/f5d470b808bc01f70978e22e595c6f7768313406
- https://git.kernel.org/stable/c/936641af564c3d92721704b781e36aaf223efdd2
- https://git.kernel.org/stable/c/718f6a56b40875f19e6915799044a02df9abfd52
- https://git.kernel.org/stable/c/11165fe2c5ea0516debe486d91df67abbe36905e
- https://git.kernel.org/stable/c/d6fd2afb137f52bf00c5210cc44d08ed54dcffb4
- https://git.kernel.org/stable/c/ef7607ab1c8adc6258fb1b27d08e26aecdc18a58
ADP enrichment
No English description supplied.
No references supplied.