misc: fastrpc: Fix incorrect DMA mapping unmap request

[ Upstream commit a2cb9cd ]

Scatterlist table is obtained during map create request and the same
table is used for DMA mapping unmap. In case there is any failure
while getting the sg_table, ERR_PTR is returned instead of sg_table.

When the map is getting freed, there is only a non-NULL check of
sg_table which will also be true in case failure was returned instead
of sg_table. This would result in improper unmap request. Add proper
check before setting map table to avoid bad unmap request.

Fixes: c68cfb7 ("misc: fastrpc: Add support for context Invoke method")
Cc: stable <stable@kernel.org>
Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20230811115643.38578-3-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/misc/fastrpc.c

@@ -711,6 +711,7 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd,
 {
 	struct fastrpc_session_ctx *sess = fl->sctx;
 	struct fastrpc_map *map = NULL;
+	struct sg_table *table;
 	int err = 0;
 
 	if (!fastrpc_map_lookup(fl, fd, ppmap, true))
@@ -736,11 +737,12 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd,
 		goto attach_err;
 	}
 
-	map->table = dma_buf_map_attachment_unlocked(map->attach, DMA_BIDIRECTIONAL);
-	if (IS_ERR(map->table)) {
-		err = PTR_ERR(map->table);
+	table = dma_buf_map_attachment_unlocked(map->attach, DMA_BIDIRECTIONAL);
+	if (IS_ERR(table)) {
+		err = PTR_ERR(table);
 		goto map_err;
 	}
+	map->table = table;
 
 	map->phys = sg_dma_address(map->table->sgl);
 	map->phys += ((u64)fl->sctx->sid << 32);