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

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Message-ID: <20251008172516.20697-1-ankitkhushwaha.linux@gmail.com>
Date: Wed,  8 Oct 2025 22:55:16 +0530
From: Ankit Khushwaha <ankitkhushwaha.linux@...il.com>
To: linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Cc: david.hunter.linux@...il.com,
	skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linuxfoundation.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Ankit Khushwaha <ankitkhushwaha.linux@...il.com>,
	syzbot+ddc001b92c083dbf2b97@...kaller.appspotmail.com
Subject: [PATCH v2] ring buffer: Propagate __rb_map_vma return value to caller

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>

Changes in v2:
* 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