Re: [PATCH v3] misc: fastrpc: Fix incorrect DMA mapping unmap request

From: Ekansh Gupta
Date: Wed Aug 02 2023 - 09:49:49 EST

On 8/2/2023 7:13 PM, Srinivas Kandagatla wrote:

On 02/08/2023 06:10, Ekansh Gupta wrote:
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

  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..de7c812 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(map->attach, DMA_BIDIRECTIONAL);

Any reason why dma_buf_map_attachment_unlocked changed to dma_buf_map_attachment?
This is a mistake from my end. My local workspace had older version due to which the function also got reverted. I will fix this in new patch. Apologies for the confusion.

+    if (IS_ERR(table)) {
+        err = PTR_ERR(table);
          goto map_err;
+    map->table = table;
      if (attr & FASTRPC_ATTR_SECUREMAP) {
          map->phys = sg_phys(map->table->sgl);