[PATCH v2] fix bit fields extraction and prevent overflow

[PATCH v2] fix bit fields extraction and prevent overflow

[Alexandra Diupina]

Add a type cast and use extract64() instead of extract32()
to avoid integer overflow on addition. Fix bit fields
extraction according to documentation.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: d3c6369a96 ("introduce xlnx-dpdma")
Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>
---
v2: fix typo
 hw/dma/xlnx_dpdma.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/hw/dma/xlnx_dpdma.c b/hw/dma/xlnx_dpdma.c
index 1f5cd64ed1..530717d188 100644
--- a/hw/dma/xlnx_dpdma.c
+++ b/hw/dma/xlnx_dpdma.c
@@ -175,24 +175,24 @@ static uint64_t xlnx_dpdma_desc_get_source_address(DPDMADescriptor *desc,
 
     switch (frag) {
     case 0:
-        addr = desc->source_address
-            + (extract32(desc->address_extension, 16, 12) << 20);
+        addr = (uint64_t)desc->source_address
+            + (extract64(desc->address_extension, 16, 16) << 32);
         break;
     case 1:
-        addr = desc->source_address2
-            + (extract32(desc->address_extension_23, 0, 12) << 8);
+        addr = (uint64_t)desc->source_address2
+            + (extract64(desc->address_extension_23, 0, 16) << 32);
         break;
     case 2:
-        addr = desc->source_address3
-            + (extract32(desc->address_extension_23, 16, 12) << 20);
+        addr = (uint64_t)desc->source_address3
+            + (extract64(desc->address_extension_23, 16, 16) << 32);
         break;
     case 3:
-        addr = desc->source_address4
-            + (extract32(desc->address_extension_45, 0, 12) << 8);
+        addr = (uint64_t)desc->source_address4
+            + (extract64(desc->address_extension_45, 0, 16) << 32);
         break;
     case 4:
-        addr = desc->source_address5
-            + (extract32(desc->address_extension_45, 16, 12) << 20);
+        addr = (uint64_t)desc->source_address5
+            + (extract64(desc->address_extension_45, 16, 16) << 32);
         break;
     default:
         addr = 0;
-- 
2.30.2

Re: [PATCH v2] fix bit fields extraction and prevent overflow

[Peter Maydell]

On Sun, 28 Apr 2024 at 19:11, Alexandra Diupina <adiupina@astralinux.ru> wrote:
>
> Add a type cast and use extract64() instead of extract32()
> to avoid integer overflow on addition. Fix bit fields
> extraction according to documentation.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: d3c6369a96 ("introduce xlnx-dpdma")
> Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>

Thanks; I've applied this to target-arm.next, and it'll go into
a pullreq sometime this week. (I tweaked the commit message to
add a bit of the context and the docs URL from the other
email thread.)

-- PMM