[PATCH v4] misc: fastrpc: Fix incorrect DMA mapping unmap request

From: Ekansh Gupta
Date: Wed Aug 02 2023 - 09:58:03 EST

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: c68cfb718c8f ("misc: fastrpc: Add support for context Invoke method")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Ekansh Gupta <quic_ekangupt@xxxxxxxxxxx>
Changes in v2:
- Added fixes information to commit text
Changes in v3:
- Set map->table only if attachment for successful
Changes in v4:
- Use correct dma buf attachment function

drivers/misc/fastrpc.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 9666d28..b2c62b2 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -756,6 +756,7 @@ 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))
@@ -783,11 +784,12 @@ 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_phys(map->table->sgl);