[PATCH v3] ring buffer: Propagate __rb_map_vma return value to caller

[PATCH v3] ring buffer: Propagate __rb_map_vma return value to caller

[Ankit Khushwaha]

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@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?id=194151be8eaebd826005329b2e123aecae714bdb
Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
---

Changes in v3: https://lore.kernel.org/linux-trace-kernel/20251008172516.20697-1-ankitkhushwaha.linux@gmail.com/
* Same as v2:)

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

---
 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)
-- 
2.51.0

Re: [PATCH v3] ring buffer: Propagate __rb_map_vma return value to caller

[Steven Rostedt]

On Thu,  9 Oct 2025 10:23:45 +0530
Ankit Khushwaha <ankitkhushwaha.linux@gmail.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@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?id=194151be8eaebd826005329b2e123aecae714bdb
> Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
> ---
> 
> Changes in v3: https://lore.kernel.org/linux-trace-kernel/20251008172516.20697-1-ankitkhushwaha.linux@gmail.com/
> * Same as v2:)
> 
> 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
> 

This is good practice, but I already pulled in v2.

-- 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)