On 6/23/2023 3:14 PM, Julia Lawall wrote:
Use array_size to protect against multiplication overflows.
The changes were done using the following Coccinelle semantic patch:
// <smpl>
@@
expression E1, E2;
constant C1, C2;
identifier alloc = {vmalloc,vzalloc};
@@
(
alloc(C1 * C2,...)
|
alloc(
- (E1) * (E2)
+ array_size(E1, E2)
,...)
)
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@xxxxxxxx>
---
drivers/bus/mhi/host/init.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index f72fcb66f408..34a543a67068 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -759,8 +759,8 @@ static int parse_ch_cfg(struct mhi_controller *mhi_cntrl,
* so to avoid any memory possible allocation failures, vzalloc is
* used here
*/
- mhi_cntrl->mhi_chan = vzalloc(mhi_cntrl->max_chan *
- sizeof(*mhi_cntrl->mhi_chan));
+ mhi_cntrl->mhi_chan = vzalloc(array_size(mhi_cntrl->max_chan,
+ sizeof(*mhi_cntrl->mhi_chan)));
if (!mhi_cntrl->mhi_chan)
return -ENOMEM;
This doesn't seem like a good fix.
If we've overflowed the multiplication, I don't think we should
continue, and the function should return an error. array_size() is
going to return SIZE_MAX, and it looks like it is possible that
vzalloc() may be able to allocate that successfully in some scenarios.
However, that is going to be less memory than parse_ch_cfg() expected to
allocate, so later on I expect the function will still corrupt memory -
basically the same result as what the unchecked overflow would do.
I'm not convinced the semantic patch is bringing value as I suspect most
of the code being patched is in the same situation.
-Jeff
