[PATCH 2/2] remoteproc: mtk_scp: Fix bounds check in mt8192_scp_da_to_va()

[Atul Akella <atul.akella@gmail.com>]

mt8192_scp_da_to_va() translates a device address to a pointer into
SCP SRAM, L1TCM or DRAM. Its bounds checks have two problems:

- (da + len) is computed in u64 and wraps for a large da or len.
  With da = 0xfffffffffffffff0 and len = 0x20, the sum is 0x10 and
  passes "<= base + size" while da >= base also holds.

- offset is an int but is assigned from a u64 difference, so it is
  truncated before being added to the region's base pointer.

da and len come from the firmware's ELF program headers
(p_paddr/p_memsz) via rproc_da_to_va(), and the returned pointer is
then written to by the ELF loader, so a malformed firmware image can
make the loader write outside the intended region.

Use a u64 offset and compare len against the remaining region size
instead of adding it to da. Apply this to the SRAM, L1TCM and DRAM
regions.

Fixes: ca23ecfdbd44 ("remoteproc/mediatek: support L1TCM")
Cc: stable@vger.kernel.org
Signed-off-by: Atul Akella <atul.akella@gmail.com>
---
 drivers/remoteproc/mtk_scp.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
index d18ae676260a..b1d83265fc26 100644
--- a/drivers/remoteproc/mtk_scp.c
+++ b/drivers/remoteproc/mtk_scp.c
@@ -775,30 +775,30 @@ static void *mt8183_scp_da_to_va(struct mtk_scp *scp, u64 da, size_t len)
 
 static void *mt8192_scp_da_to_va(struct mtk_scp *scp, u64 da, size_t len)
 {
-	int offset;
+	u64 offset;
 	const struct mtk_scp_sizes_data *scp_sizes;
 
 	scp_sizes = scp->data->scp_sizes;
-	if (da >= scp->sram_phys &&
-	    (da + len) <= scp->sram_phys + scp->sram_size) {
+	if (da >= scp->sram_phys) {
 		offset = da - scp->sram_phys;
-		return (void __force *)scp->sram_base + offset;
+		if (offset <= scp->sram_size && len <= scp->sram_size - offset)
+			return (void __force *)scp->sram_base + offset;
 	}
 
 	/* optional memory region */
-	if (scp->cluster->l1tcm_size &&
-	    da >= scp->cluster->l1tcm_phys &&
-	    (da + len) <= scp->cluster->l1tcm_phys + scp->cluster->l1tcm_size) {
+	if (scp->cluster->l1tcm_size && da >= scp->cluster->l1tcm_phys) {
 		offset = da - scp->cluster->l1tcm_phys;
-		return (void __force *)scp->cluster->l1tcm_base + offset;
+		if (offset <= scp->cluster->l1tcm_size &&
+		    len <= scp->cluster->l1tcm_size - offset)
+			return (void __force *)scp->cluster->l1tcm_base + offset;
 	}
 
 	/* optional memory region */
-	if (scp_sizes->max_dram_size &&
-	    da >= scp->dma_addr &&
-	    (da + len) <= scp->dma_addr + scp_sizes->max_dram_size) {
+	if (scp_sizes->max_dram_size && da >= scp->dma_addr) {
 		offset = da - scp->dma_addr;
-		return scp->cpu_addr + offset;
+		if (offset <= scp_sizes->max_dram_size &&
+		    len <= scp_sizes->max_dram_size - offset)
+			return scp->cpu_addr + offset;
 	}
 
 	return NULL;
-- 
2.43.0