Re: [PATCH] virtio_console: pass gfp flag through in alloc_buf()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Sat, Aug 29, 2026 at 09:20:39AM +0800, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> The `gfp` parameter of alloc_buf() has been dead code since the
> function was introduced. The underlying allocation was always
> hardcoded to GFP_KERNEL - first via kmalloc(..., GFP_KERNEL), then
> via kmalloc_flex(*buf, sg, pages, GFP_KERNEL), and most recently
> via kmalloc_flex(*buf, sg, pages) which defaults to GFP_KERNEL.
> 
> This causes a "sleeping function called from invalid context" BUG
> when the hvc console flush path calls put_chars() with IRQs
> disabled:
> 
>   BUG: sleeping function called from invalid context at \
>        include/linux/sched/mm.h:322
>   in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 416, \
> 	       name: test_progs
>   ...
>   Call Trace:
>    __kmalloc_noprof+0x468/0x7c0
>    alloc_buf.isra.0+0x42/0x260
>    put_chars+0x1e5/0x2f0
>    hvc_console_print+0x29d/0x6e0
>    console_emit_next_record+0x21d/0x480
>    console_flush_one_record+0x431/0x6a0
>    console_unlock+0xda/0x1c0
>    vprintk_emit+0x300/0x350
> 
> put_chars() correctly passes GFP_ATOMIC, but alloc_buf() silently
> discards it and allocates with GFP_KERNEL, which may sleep.
> 
> Pass the caller-supplied gfp flag through to kmalloc_flex() so
> that atomic callers get atomic allocations.
> 
> Fixes: 69050f8d6d07 ("treewide: Replace kmalloc with kmalloc_obj for non-scalar types")
> Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>

Sorry for the delay, I took this earlier patch instead:
	https://lore.kernel.org/r/20260810-serial-v1-1-abbe51602c13@debian.org