linux-kernel - [PATCH 3/3] misc: fastrpc: Fix copy buffer page size

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Message-Id: <20250110134239.123603-4-srinivas.kandagatla@linaro.org>
Date: Fri, 10 Jan 2025 13:42:39 +0000
From: srinivas.kandagatla@...aro.org
To: gregkh@...uxfoundation.org
Cc: linux-kernel@...r.kernel.org,
	Ekansh Gupta <quic_ekangupt@...cinc.com>,
	stable@...nel.org,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: [PATCH 3/3] misc: fastrpc: Fix copy buffer page size

From: Ekansh Gupta <quic_ekangupt@...cinc.com>

For non-registered buffer, fastrpc driver copies the buffer and
pass it to the remote subsystem. There is a problem with current
implementation of page size calculation which is not considering
the offset in the calculation. This might lead to passing of
improper and out-of-bounds page size which could result in
memory issue. Calculate page start and page end using the offset
adjusted address instead of absolute address.

Fixes: 02b45b47fbe8 ("misc: fastrpc: fix remote page size calculation")
Cc: stable@...nel.org
Signed-off-by: Ekansh Gupta <quic_ekangupt@...cinc.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
---
 drivers/misc/fastrpc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 891529aa9069..e567a36275af 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1019,8 +1019,8 @@ static int fastrpc_get_args(u32 kernel, struct fastrpc_invoke_ctx *ctx)
 					(pkt_size - rlen);
 			pages[i].addr = pages[i].addr &	PAGE_MASK;
 
-			pg_start = (args & PAGE_MASK) >> PAGE_SHIFT;
-			pg_end = ((args + len - 1) & PAGE_MASK) >> PAGE_SHIFT;
+			pg_start = (rpra[i].buf.pv & PAGE_MASK) >> PAGE_SHIFT;
+			pg_end = ((rpra[i].buf.pv + len - 1) & PAGE_MASK) >> PAGE_SHIFT;
 			pages[i].size = (pg_end - pg_start + 1) * PAGE_SIZE;
 			args = args + mlen;
 			rlen -= mlen;
-- 
2.25.1