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ring-buffer: Do not let subbuf be bigger than write mask

Message ID 20240220095112.77e9cb81@gandalf.local.home (mailing list archive)
State Accepted
Commit e78fb4eac817308027da88d02e5d0213462a7562
Headers show
Series ring-buffer: Do not let subbuf be bigger than write mask | expand

Commit Message

Steven Rostedt Feb. 20, 2024, 2:51 p.m. UTC 
From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The data on the subbuffer is measured by a write variable that also
contains status flags. The counter is just 20 bits in length. If the
subbuffer is bigger than then counter, it will fail.

Make sure that the subbuffer can not be set to greater than the counter
that keeps track of the data on the subbuffer.

Fixes: 2808e31ec12e5 ("ring-buffer: Add interface for configuring trace sub buffer size")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 4 ++++
 1 file changed, 4 insertions(+)
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Patch

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index aa54266f5e1f..3852f3b001cc 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5878,6 +5878,10 @@  int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
 	if (psize <= BUF_PAGE_HDR_SIZE)
 		return -EINVAL;
 
+	/* Size of a subbuf cannot be greater than the write counter */
+	if (psize > RB_WRITE_MASK + 1)
+		return -EINVAL;
+
 	old_order = buffer->subbuf_order;
 	old_size = buffer->subbuf_size;