ALSA: seq: Fix division by zero in initialize_timer()
Summary
| CVE | CVE-2026-74504 |
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| State | PUBLISHED |
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| Assigner | Linux |
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| Source Priority | CVE Program / NVD first with legacy fallback |
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| Published | 2026-08-15 13:17:55 UTC |
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| Updated | 2026-08-15 13:17:55 UTC |
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| Description | 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
tmr->ticks = 1000000000 / (r * freq);
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. |
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Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|
| CNA |
Linux |
Linux |
affected 37745918e0e7575bc40f38da93a99b9fa6406224 d0e19932875746118e298b4c974f3b2d4aeb16fc git |
Not specified |
| CNA |
Linux |
Linux |
affected 37745918e0e7575bc40f38da93a99b9fa6406224 5260e195c53e898a4a76527d4bb2178f31795e78 git |
Not specified |
| CNA |
Linux |
Linux |
affected 37745918e0e7575bc40f38da93a99b9fa6406224 42c6543ff27ea280334244458d4f52ec7133cc05 git |
Not specified |
| CNA |
Linux |
Linux |
affected 37745918e0e7575bc40f38da93a99b9fa6406224 21e19688433452dfbbbe6b2bb670dea6eb92f0f6 git |
Not specified |
| CNA |
Linux |
Linux |
affected 6.12 |
Not specified |
| CNA |
Linux |
Linux |
unaffected 6.12 semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 6.12.103 6.12.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 6.18.44 6.18.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 7.1.8 7.1.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 7.2-rc6 * original_commit_for_fix |
Not specified |
References
| Reference | Source | Link | Tags |
|---|
| git.kernel.org/stable/c/5260e195c53e898a4a76527d4bb2178f31795e78 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/42c6543ff27ea280334244458d4f52ec7133cc05 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/21e19688433452dfbbbe6b2bb670dea6eb92f0f6 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/d0e19932875746118e298b4c974f3b2d4aeb16fc |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| CVE Program record |
CVE.ORG |
www.cve.org |
canonical |
| NVD vulnerability detail |
NVD |
nvd.nist.gov |
canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.