Re: [Devel] [PATCH hci-8.1 1/6] ve/printk: Add sanity checks in ve_printk functions

[no-reply@sashiko.virtuozzo.com]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] printk: WARN_ON_ONCE() in ve_vprintk_deferred() uses non-deferred printk path
--

commit 2b22fc2da5243bd2b5c695100f66ab107b28c158
Author: Vladimir Riabchun <vladimir.riabchun@virtuozzo.com>

ve/printk: Add sanity checks in ve_printk functions

This patch adds a sanity check on the dst argument in the ve_printk
helpers. It also reorders the VE_LOG test so the dst bit is checked
before ve_is_super().

Link: https://virtuozzo.atlassian.net/browse/VSTOR-146839

> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c

[ ... ]

> @@ -2567,10 +2569,12 @@ static asmlinkage int ve_vprintk_deferred(int dst, const char *fmt, va_list args
>  	va_list args2;
>  	int r = 0;
>  
> +	WARN_ON_ONCE(!dst || (dst & ~VE_LOG_BOTH));
> +
>  	va_copy(args2, args);
>  	if (ve_is_super(get_exec_env()) || (dst & VE0_LOG))
>  		r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args);

[Severity: Low]
This isn't a bug in the normal case, but is the new WARN_ON_ONCE() safe
in ve_vprintk_deferred()?

This function exists for contexts where the regular printk path is
unsafe, which is why it emits at LOGLEVEL_SCHED through vprintk_emit().
WARN_ON_ONCE() reports through the normal printk and console path. It
can also panic if panic_on_warn is set.

If a caller passes dst == 0 or a dst with bits outside VE_LOG_BOTH from
such a context, could the warning recurse into scheduler or console
locks that the deferred variant is meant to avoid?

I did not find a caller that passes an invalid dst. The trigger would
need a buggy caller, and the warning fires only once.

Would a BUILD_BUG_ON() for constant arguments be more suitable here?
Alternatively, the report could go through a deferred-safe mechanism
such as printk_deferred().

-- 
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261002-ve-printk-irq-v1-0-cb55896d455c@virtuozzo.com?part=1

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