From: GitHub issues - opened <github@alsa-project.org>
To: alsa-devel@alsa-project.org
Subject: alsamixer: segfault in display_controls()
Date: Fri, 28 Aug 2026 18:39:56 +0200 (CEST) [thread overview]
Message-ID: <18d00595a73abf00-webhooks-bot@alsa-project.org> (raw)
In-Reply-To: <18d00595a7166c00-webhooks-bot@alsa-project.org>
alsa-project/alsa-utils issue #335 was opened from fenugrec:
I think I know what sequence triggers this.
*** steps to reproduce
1- connect a device that has no Capture controls (unclear if this is the crucial difference). Here this is a Presonus Studio 1824c
2- run alsamixer; F6 to select that Card
3- Go the Capture view (F4)
4- arrow right
5- go to All view (F5) -> segfault
*** backtrace
```
#0 display_control (control_index=0xffffffff) at /usr/src/debug/alsa-utils/alsa-utils-1.2.16/alsamixer/mixer_display.c:421
control = 0x55855558ff60
col = 0x0
i = <optimized out>
c = <optimized out>
left = 0x2
frame_left = 0xb
bar_height = <optimized out>
volumes = {0, 6.9531436082559572e-310}
switches = {0x0, 0x0}
index = 0x555a0710
s = <optimized out>
buf = "\360\030_UUU\000\000\003\000\000\000UU", '\000' <repeats 11 times>, "\230z\021\003\000\000\000\b\000\000\000\a\000\000\000\003\000\000\000UU\000\000\2352VUUU\000\000\2462VUUU\000"
err = <optimized out>
#1 display_controls () at /usr/src/debug/alsa-utils/alsa-utils-1.2.16/alsamixer/mixer_display.c:674
i = 0x0
#2 0x00005555555585dc in mainloop () at /usr/src/debug/alsa-utils/alsa-utils-1.2.16/alsamixer/mainloop.c:146
pollfds = 0x55555560e790
nfds = 0x2
n = <optimized out>
active_widget = 0x5555555676e0 <mixer_widget>
revents = 0x1
key = <optimized out>
err = <optimized out>
#3 main (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/alsa-utils/alsa-utils-1.2.16/alsamixer/cli.c:176
No locals.
```
The problem is the argument `control_index=0xffffffff` which comes from display_controls() around lines 660-670 ; in this debug run (after the segfault) I observe the following values
```
(gdb) p first_visible_control_index
$1 = 0xffffffff
(gdb) p controls_count
$2 = 0x5
(gdb) p visible_controls
$3 = 0x5
(gdb) p focus_control_index
$4 = 0x0
```
not sure why `first_visible_control_index` has that value...
Issue URL : https://github.com/alsa-project/alsa-utils/issues/335
Repository URL: https://github.com/alsa-project/alsa-utils
parent reply other threads:[~2026-08-28 16:40 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <18d00595a7166c00-webhooks-bot@alsa-project.org>]
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