From 987b0ff1b9d9b8ee9fa3a5a64c62a4475d18d313 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Tue, 27 Dec 2022 15:27:39 +0100
Subject: [PATCH] lib/mpi: Fix buffer overrun when SG is too long

[ Upstream commit 7361d1bc307b926cbca214ab67b641123c2d6357 ]

The helper mpi_read_raw_from_sgl sets the number of entries in
the SG list according to nbytes.  However, if the last entry
in the SG list contains more data than nbytes, then it may overrun
the buffer because it only allocates enough memory for nbytes.

Fixes: 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers")
Reported-by: Roberto Sassu <roberto.sassu@huaweicloud.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 lib/mpi/mpicoder.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index eead4b339466..4f73db248009 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -397,7 +397,8 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
 
 	while (sg_miter_next(&miter)) {
 		buff = miter.addr;
-		len = miter.length;
+		len = min_t(unsigned, miter.length, nbytes);
+		nbytes -= len;
 
 		for (x = 0; x < len; x++) {
 			a <<= 8;