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Date:   Sun,  5 Sep 2021 16:40:54 +0200
From:   Len Baker <len.baker@....com>
To:     Boris Brezillon <boris.brezillon@...labora.com>,
        Nicolas Pitre <npitre@...libre.com>
Cc:     Len Baker <len.baker@....com>, Kees Cook <keescook@...omium.org>,
        linux-i3c@...ts.infradead.org, linux-hardening@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] i3c/master/mipi-i3c-hci: Prefer struct_size over open coded arithmetic

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@....com>
---
 drivers/i3c/master/mipi-i3c-hci/dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
index af873a9be050..2990ac9eaade 100644
--- a/drivers/i3c/master/mipi-i3c-hci/dma.c
+++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
@@ -223,7 +223,7 @@ static int hci_dma_init(struct i3c_hci *hci)
 	}
 	if (nr_rings > XFER_RINGS)
 		nr_rings = XFER_RINGS;
-	rings = kzalloc(sizeof(*rings) + nr_rings * sizeof(*rh), GFP_KERNEL);
+	rings = kzalloc(struct_size(rings, headers, nr_rings), GFP_KERNEL);
 	if (!rings)
 		return -ENOMEM;
 	hci->io_data = rings;
--
2.25.1

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