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435990e25b
snd_seq_event_dup() copies an incoming event into a pool cell and, in
the UMP-enabled build, clears the trailing cell->ump.raw.extra word that
the memcpy() did not cover. The guard deciding whether to clear it
compares the copied size against sizeof(cell->event):
memcpy(&cell->ump, event, size);
if (size < sizeof(cell->event))
cell->ump.raw.extra = 0;
For a legacy (non-UMP) event, size == sizeof(struct snd_seq_event) ==
sizeof(cell->event), so the condition is false and the extra word keeps
stale data. The cell pool is allocated with kvmalloc() (not zeroed) and
cells are reused via a free list, so that word holds uninitialised heap
or leftover event data.
When such a cell is delivered to a UMP client (client->midi_version > 0)
that set SNDRV_SEQ_FILTER_NO_CONVERT -- so the legacy event reaches it
unconverted -- snd_seq_read() reads it out as the larger struct
snd_seq_ump_event and copies the stale word to user space, a 4-byte
kernel heap infoleak to an unprivileged /dev/snd/seq client.
Compare against sizeof(cell->ump) instead, so the trailing word is zeroed
for every event shorter than the UMP cell.
Fixes:
|
||
|---|---|---|
| .. | ||
| oss | ||
| Kconfig | ||
| Makefile | ||
| seq_clientmgr.c | ||
| seq_clientmgr.h | ||
| seq_compat.c | ||
| seq_dummy.c | ||
| seq_fifo.c | ||
| seq_fifo.h | ||
| seq_info.c | ||
| seq_info.h | ||
| seq_lock.c | ||
| seq_lock.h | ||
| seq_memory.c | ||
| seq_memory.h | ||
| seq_midi_emul.c | ||
| seq_midi_event.c | ||
| seq_midi.c | ||
| seq_ports.c | ||
| seq_ports.h | ||
| seq_prioq.c | ||
| seq_prioq.h | ||
| seq_queue.c | ||
| seq_queue.h | ||
| seq_system.c | ||
| seq_system.h | ||
| seq_timer.c | ||
| seq_timer.h | ||
| seq_ump_client.c | ||
| seq_ump_convert.c | ||
| seq_ump_convert.h | ||
| seq_virmidi.c | ||
| seq.c | ||