[PATCH 2/4] misc: fastrpc: fix DMA address corruption due to find_vma misuse

[PATCH 2/4] misc: fastrpc: fix DMA address corruption due to find_vma misuse

[srini]

From: Junrui Luo <moonafterrain@outlook.com>

fastrpc_get_args() uses find_vma() to look up the VMA for a user-provided
pointer and compute a DMA address offset. When the address falls in a gap
before the returned VMA, (ptr & PAGE_MASK) - vma->vm_start underflows,
corrupting the DMA address sent to the DSP.

Replace find_vma() with vma_lookup(), which returns NULL when the address
is not contained within any VMA.

Cc: stable@vger.kernel.org
Fixes: 80f3afd72bd4 ("misc: fastrpc: consider address offset before sending to DSP")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Srinivas Kandagatla <srini@kernel.org>
---
 drivers/misc/fastrpc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 48f8262af539..cca7489605c5 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1090,7 +1090,7 @@ static int fastrpc_get_args(u32 kernel, struct fastrpc_invoke_ctx *ctx)
 			pages[i].addr = ctx->maps[i]->dma_addr;
 
 			mmap_read_lock(current->mm);
-			vma = find_vma(current->mm, ctx->args[i].ptr);
+			vma = vma_lookup(current->mm, ctx->args[i].ptr);
 			if (vma)
 				pages[i].addr += (ctx->args[i].ptr & PAGE_MASK) -
 						 vma->vm_start;
-- 
2.53.0

[PATCH 3/4] misc: fastrpc: Fix NULL pointer dereference in rpmsg callback

[srini]

From: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>

A NULL pointer dereference was observed on Hawi at boot when the DSP
sends a glink message before fastrpc_rpmsg_probe() has completed
initialization:

  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000178
  pc : _raw_spin_lock_irqsave+0x34/0x8c
  lr : fastrpc_rpmsg_callback+0x3c/0xcc [fastrpc]
  ...
  Call trace:
   _raw_spin_lock_irqsave+0x34/0x8c (P)
   fastrpc_rpmsg_callback+0x3c/0xcc [fastrpc]
   qcom_glink_native_rx+0x538/0x6a4
   qcom_glink_smem_intr+0x14/0x24 [qcom_glink_smem]

The faulting address 0x178 corresponds to the lock variable inside
struct fastrpc_channel_ctx, confirming that cctx is NULL when
fastrpc_rpmsg_callback() attempts to take the spinlock.

There are two issues here. First, dev_set_drvdata() is called before
spin_lock_init() and idr_init(), leaving a window where the callback
can retrieve a valid cctx pointer but operate on an uninitialized
spinlock. Second, the rpmsg channel becomes live as soon as the driver
is bound, so fastrpc_rpmsg_callback() can fire before dev_set_drvdata()
is called at all, resulting in dev_get_drvdata() returning NULL.

Fix both issues by moving all cctx initialization ahead of
dev_set_drvdata() so the structure is fully initialized before it
becomes visible to the callback, and add a NULL check in
fastrpc_rpmsg_callback() as a guard against any remaining window.

Fixes: f6f9279f2bf0 ("misc: fastrpc: Add Qualcomm fastrpc basic driver model")
Cc: stable@vger.kernel.org
Signed-off-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
Reviewed-by: Bjorn Andersson <andersson@kernel.org>
Signed-off-by: Srinivas Kandagatla <srini@kernel.org>
---
 drivers/misc/fastrpc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index cca7489605c5..47cf3d21b51d 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -2460,7 +2460,6 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 
 	kref_init(&data->refcount);
 
-	dev_set_drvdata(&rpdev->dev, data);
 	rdev->dma_mask = &data->dma_mask;
 	dma_set_mask_and_coherent(rdev, DMA_BIT_MASK(32));
 	INIT_LIST_HEAD(&data->users);
@@ -2469,6 +2468,7 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 	idr_init(&data->ctx_idr);
 	data->domain_id = domain_id;
 	data->rpdev = rpdev;
+	dev_set_drvdata(&rpdev->dev, data);
 
 	err = of_platform_populate(rdev->of_node, NULL, NULL, rdev);
 	if (err)
@@ -2542,6 +2542,9 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device *rpdev, void *data,
 	if (len < sizeof(*rsp))
 		return -EINVAL;
 
+	if (!cctx)
+		return -ENODEV;
+
 	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 4);
 
 	spin_lock_irqsave(&cctx->lock, flags);
-- 
2.53.0

[PATCH 4/4] misc: fastrpc: fix use-after-free race in fastrpc_map_create

[srini]

From: Zhenghang Xiao <kipreyyy@gmail.com>

fastrpc_map_lookup returns a raw pointer after releasing fl->lock. The
caller fastrpc_map_create then calls fastrpc_map_get (kref_get_unless_zero)
on this unprotected pointer. A concurrent MEM_UNMAP can free the map
between the lock release and the kref operation, resulting in a
use-after-free on the freed slab object.

Restore the take_ref parameter to fastrpc_map_lookup so the reference
is acquired atomically under fl->lock before the pointer is exposed to
the caller.

Fixes: 10df039834f8 ("misc: fastrpc: Skip reference for DMA handles")
Cc: stable@vger.kernel.org
Signed-off-by: Zhenghang Xiao <kipreyyy@gmail.com>
Signed-off-by: Srinivas Kandagatla <srini@kernel.org>
---
 drivers/misc/fastrpc.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 47cf3d21b51d..f3a49384586d 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -388,7 +388,7 @@ static int fastrpc_map_get(struct fastrpc_map *map)
 
 
 static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd,
-			    struct fastrpc_map **ppmap)
+			    struct fastrpc_map **ppmap, bool take_ref)
 {
 	struct fastrpc_map *map = NULL;
 	struct dma_buf *buf;
@@ -403,6 +403,12 @@ static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd,
 		if (map->fd != fd || map->buf != buf)
 			continue;
 
+		if (take_ref) {
+			ret = fastrpc_map_get(map);
+			if (ret)
+				break;
+		}
+
 		*ppmap = map;
 		ret = 0;
 		break;
@@ -920,19 +926,10 @@ static int fastrpc_map_attach(struct fastrpc_user *fl, int fd,
 static int fastrpc_map_create(struct fastrpc_user *fl, int fd,
 			      u64 len, u32 attr, struct fastrpc_map **ppmap)
 {
-	struct fastrpc_session_ctx *sess = fl->sctx;
-	int err = 0;
-
-	if (!fastrpc_map_lookup(fl, fd, ppmap)) {
-		if (!fastrpc_map_get(*ppmap))
-			return 0;
-		dev_dbg(sess->dev, "%s: Failed to get map fd=%d\n",
-			__func__, fd);
-	}
-
-	err = fastrpc_map_attach(fl, fd, len, attr, ppmap);
+	if (!fastrpc_map_lookup(fl, fd, ppmap, true))
+		return 0;
 
-	return err;
+	return fastrpc_map_attach(fl, fd, len, attr, ppmap);
 }
 
 /*
@@ -1202,7 +1199,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx,
 	for (i = 0; i < FASTRPC_MAX_FDLIST; i++) {
 		if (!fdlist[i])
 			break;
-		if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap))
+		if (!fastrpc_map_lookup(fl, (int)fdlist[i], &mmap, false))
 			fastrpc_map_put(mmap);
 	}
 
-- 
2.53.0