linux-hardening - Re: [PATCH][next] scsi: sd: Avoid -Wflex-array-member-not-at-end warning

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Message-ID: <aBOI-cmnvqMjV0yX@infradead.org>
Date: Thu, 1 May 2025 07:45:13 -0700
From: Christoph Hellwig <hch@...radead.org>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] scsi: sd: Avoid -Wflex-array-member-not-at-end
 warning

Yikes.  This is way to ugly to live.  Just remove the silly flex
array entirely and everyone is better off:

diff --git a/drivers/scsi/scsi_proto_test.c b/drivers/scsi/scsi_proto_test.c
index c093389edabb..2fc5c6523184 100644
--- a/drivers/scsi/scsi_proto_test.c
+++ b/drivers/scsi/scsi_proto_test.c
@@ -30,14 +30,6 @@ static void test_scsi_proto(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, get_unaligned_be16(&ss.s.stream_identifier),
 			0x1234);
 	KUNIT_EXPECT_EQ(test, ss.s.rel_lifetime + 0, 0x3f);
-
-	static const union {
-		struct scsi_stream_status_header h;
-		u8 arr[sizeof(struct scsi_stream_status_header)];
-	} sh = { .arr = { 1, 2, 3, 4, 0, 0, 5, 6 } };
-	KUNIT_EXPECT_EQ(test, get_unaligned_be32(&sh.h.len), 0x1020304);
-	KUNIT_EXPECT_EQ(test, get_unaligned_be16(&sh.h.number_of_open_streams),
-			0x506);
 }
 
 static struct kunit_case scsi_proto_test_cases[] = {
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 950d8c9fb884..3f6e87705b62 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3215,7 +3215,7 @@ static bool sd_is_perm_stream(struct scsi_disk *sdkp, unsigned int stream_id)
 		return false;
 	if (get_unaligned_be32(&buf.h.len) < sizeof(struct scsi_stream_status))
 		return false;
-	return buf.h.stream_status[0].perm;
+	return buf.s.perm;
 }
 
 static void sd_read_io_hints(struct scsi_disk *sdkp, unsigned char *buffer)
diff --git a/include/scsi/scsi_proto.h b/include/scsi/scsi_proto.h
index aeca37816506..bc8f2b2226be 100644
--- a/include/scsi/scsi_proto.h
+++ b/include/scsi/scsi_proto.h
@@ -349,7 +349,6 @@ struct scsi_stream_status_header {
 	__be32 len;	/* length in bytes of stream_status[] array. */
 	u16 reserved;
 	__be16 number_of_open_streams;
-	DECLARE_FLEX_ARRAY(struct scsi_stream_status, stream_status);
 };
 
 static_assert(sizeof(struct scsi_stream_status_header) == 8);