[PATCH] blktrace: reject buf_size smaller than blk_io_trace

[Deepanshu Kartikey]

blk_trace_setup() accepts any non-zero buf_size.
If buf_size < sizeof(struct blk_io_trace), relay_reserve()
always returns NULL and all trace events are silently dropped.

Reject such values early with -EINVAL.

Reported-by: syzbot+ed8bc247f231c1a48e21@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=ed8bc247f231c1a48e21
Signed-off-by: Deepanshu Kartikey <Kartikey406@xxxxxxxxx>
---
 kernel/trace/blktrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 8cd2520b4c99..6cc7d83ed1c2 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -773,7 +773,7 @@ int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	if (ret)
 		return -EFAULT;
 
-	if (!buts.buf_size || !buts.buf_nr)
+	if (buts.buf_size < sizeof(struct blk_io_trace) || !buts.buf_nr)
 		return -EINVAL;
 
 	buts2 = (struct blk_user_trace_setup2) {
-- 
2.43.0