Re: [PATCH 6.12 000/565] 6.12.58-rc1 review

[Jari Ruusu]

Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> This is the start of the stable review cycle for the 6.12.58 release.
> There are 565 patches in this series, all will be posted as a response
> to this one.  If anyone has any issues with these being applied, please
> let me know.
[SNIP]
> Zizhi Wo <wozizhi@xxxxxxxxxxxxxxx>
>     tty/vt: Add missing return value for VT_RESIZE in vt_ioctl()
 
Locking seems to be messed up in backport of above mentioned patch.
 
That patch is viewable here:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/commit/?h=queue/6.12&id=884e9ac7361b2a3c3a7a90ffaf541ffc2ded6738

Upstream uses guard() locking:
|    case VT_RESIZE:
|    {
|        ....
|        guard(console_lock)();
|        ^^^^^^^^^^^^^^^^^^^^^-------this generates auto-unlock code
|        ....
|        ret = __vc_resize(vc_cons[i].d, cc, ll, true);
|        if (ret)
|            return ret;
|            ^^^^^^^^^^----------this releases console lock
|        ....
|        break;    
|    }
 
Older stable branches use old-school locking:
|    case VT_RESIZE:
|    {
|        ....
|        console_lock();
|        ....
|        ret = __vc_resize(vc_cons[i].d, cc, ll, true);
|        if (ret)
|            return ret;
|            ^^^^^^^^^^----------this does not release console lock
|        ....
|        console_unlock();
|        break;
|    }
 
Backporting upstream fixes that use guard() locking to older stable
branches that use old-school locking need "extra sports".
 
Please consider dropping or fixing above mentioned patch.

--
Jari Ruusu  4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD  ACDF F073 3C80 8132 F189