CVE-2026-74504 PUBLISHED

ALSA: seq: Fix division by zero in initialize_timer()

Assigner: Linux
Reserved: 15.08.2026 Published: 15.08.2026 Updated: 15.08.2026

In the Linux kernel, the following vulnerability has been resolved:

ALSA: seq: Fix division by zero in initialize_timer()

A userspace-driven ALSA timer (SND_UTIMER) lets an unprivileged user set the backing snd_timer's hardware resolution to an arbitrary 64-bit value via SNDRV_TIMER_IOCTL_CREATE. snd_utimer_create() only rejects zero.

When such a timer is bound to a sequencer queue, initialize_timer() computes the tick period as

<pre>tmr->ticks = 1000000000 / (r * freq); </pre>

where r is that user-controlled resolution and freq is the sequencer update rate in Hz, clamped to MIN_FREQUENCY..MAX_FREQUENCY (10..6250). A resolution of 2^63 makes the 64-bit product r * freq wrap to zero for any even freq, including DEFAULT_FREQUENCY (1000), so the division faults with a divide-by-zero.

The division runs under tmr->lock with interrupts disabled, so the oops leaves the spinlock held and hangs the CPU. It is reachable by an unprivileged user with access to /dev/snd/timer and /dev/snd/seq.

Oops: divide error: 0000 [#1] SMP KASAN PTI CPU: 7 UID: 1000 PID: 456 Comm: alsa_seq_utimer Not tainted 7.2.0-rc4+ RIP: 0010:initialize_timer.constprop.0+0x20a/0x2d0 snd_seq_timer_start+0x15e/0x2b0 snd_seq_control_queue+0x56f/0xba0 snd_seq_write+0x3e0/0x730

Reject an overflowing product with check_mul_overflow() and fall back to a single tick, which also avoids feeding a wrapped-but-nonzero divisor (e.g. 2^63 * 1000 mod 2^64 == 0, or other resolutions wrapping to a small value) into the period computation.

Product Status

Vendor Linux
Product Linux
Versions Default: unaffected
  • affected from 37745918e0e7575bc40f38da93a99b9fa6406224 to d0e19932875746118e298b4c974f3b2d4aeb16fc (excl.)
  • affected from 37745918e0e7575bc40f38da93a99b9fa6406224 to 5260e195c53e898a4a76527d4bb2178f31795e78 (excl.)
  • affected from 37745918e0e7575bc40f38da93a99b9fa6406224 to 42c6543ff27ea280334244458d4f52ec7133cc05 (excl.)
  • affected from 37745918e0e7575bc40f38da93a99b9fa6406224 to 21e19688433452dfbbbe6b2bb670dea6eb92f0f6 (excl.)
Vendor Linux
Product Linux
Versions Default: affected
  • Version 6.12 is affected
  • unaffected from 0 to 6.12 (excl.)
  • unaffected from 6.12.103 to 6.12.* (incl.)
  • unaffected from 6.18.44 to 6.18.* (incl.)
  • unaffected from 7.1.8 to 7.1.* (incl.)
  • unaffected from 7.2-rc6 to * (incl.)

References