linux-kernel - Re: [PATCH v2] ring buffer: Propagate __rb_map

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Message-ID: <20251008221109.13a76717@batman.local.home>
Date: Wed, 8 Oct 2025 22:11:09 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Ankit Khushwaha <ankitkhushwaha.linux@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 david.hunter.linux@...il.com, skhan@...uxfoundation.org,
 linux-kernel-mentees@...ts.linuxfoundation.org, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 syzbot+ddc001b92c083dbf2b97@...kaller.appspotmail.com
Subject: Re: [PATCH v2] ring buffer: Propagate __rb_map_vma return value to
 caller

On Wed,  8 Oct 2025 22:55:16 +0530
Ankit Khushwaha <ankitkhushwaha.linux@...il.com> wrote:

> The return value from `__rb_map_vma()`, which rejects writable or
> executable mappings (VM_WRITE, VM_EXEC, or !VM_MAYSHARE), was being
> ignored. As a result the caller of `__rb_map_vma` always returned 0 
> even when the mapping had actually failed, allowing it to proceed
> with an invalid VMA.
> 
> Reported-by: syzbot+ddc001b92c083dbf2b97@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?id=194151be8eaebd826005329b2e123aecae714bdb
> Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@...il.com>
> 

Thanks for the update.

> Changes in v2:
> * applied minor cleanup suggested by Steve in v1

Note, the "changes" should be below the "---" as that prevents it from
being added to the git change log. And it's always good to include a
link to the previous version.

For example:

> 
> ---

Changes in v2: https://lore.kernel.org/linux-trace-kernel/20251007171256.20884-1-ankitkhushwaha.linux@gmail.com/
* applied minor cleanup suggested by Steve in v1

-- Steve


>  kernel/trace/ring_buffer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 43460949ad3f..1244d2c5c384 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -7273,7 +7273,7 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu,
>  		atomic_dec(&cpu_buffer->resize_disabled);
>  	}
>  
> -	return 0;
> +	return err;
>  }
>  
>  int ring_buffer_unmap(struct trace_buffer *buffer, int cpu)